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	$136.43	3.727%	$141.5147	$141.51	$141.50	$141.50
Purchase #2	$149.25	5.117%	$156.8871	$156.89	$156.90	$156.90
Purchase #3	$69.60	11.741%	$77.7717	$77.77	$77.75	$77.80
Purchase #4	$114.26	8.154%	$123.5768	$123.58	$123.60	$123.60
Purchase #5	$204.89	11.594%	$228.6449	$228.64	$228.65	$228.60
Purchase #6	$156.44	6.803%	$167.0826	$167.08	$167.10	$167.10
Purchase #7	$243.77	9.683%	$267.3742	$267.37	$267.35	$267.40
7 purchase totals =	$1,074.64		$1,162.8520	$1,162.84	$1,162.85	$1,162.90