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	$150.51	5.274%	$158.4479	$158.45	$158.45	$158.40
Purchase #2	$78.81	8.478%	$85.4915	$85.49	$85.50	$85.50
Purchase #3	$106.91	6.233%	$113.5737	$113.57	$113.55	$113.60
Purchase #4	$107.68	10.474%	$118.9584	$118.96	$118.95	$119.00
Purchase #5	$211.74	10.695%	$234.3856	$234.39	$234.40	$234.40
Purchase #6	$167.43	13.857%	$190.6308	$190.63	$190.65	$190.60
Purchase #7	$52.59	12.713%	$59.2758	$59.28	$59.30	$59.30
7 purchase totals =	$875.67		$960.7637	$960.77	$960.80	$960.80