Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$122.54	8.440%	$132.8824	$132.88	$132.90	$132.90
Purchase #2	$132.81	12.258%	$149.0898	$149.09	$149.10	$149.10
Purchase #3	$162.51	6.590%	$173.2194	$173.22	$173.20	$173.20
Purchase #4	$204.26	6.190%	$216.9037	$216.90	$216.90	$216.90
Purchase #5	$152.85	9.686%	$167.6551	$167.66	$167.65	$167.70
Purchase #6	$108.36	3.113%	$111.7332	$111.73	$111.75	$111.70
Purchase #7	$186.89	7.428%	$200.7722	$200.77	$200.75	$200.80
7 purchase totals =	$1,070.22		$1,152.2558	$1,152.25	$1,152.25	$1,152.30