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	$190.29	3.163%	$196.3089	$196.31	$196.30	$196.30
Purchase #2	$26.58	6.408%	$28.2832	$28.28	$28.30	$28.30
Purchase #3	$221.63	8.834%	$241.2088	$241.21	$241.20	$241.20
Purchase #4	$29.33	10.590%	$32.436	$32.44	$32.45	$32.40
Purchase #5	$127.50	12.866%	$143.9042	$143.90	$143.90	$143.90
Purchase #6	$88.50	9.800%	$97.173	$97.17	$97.15	$97.20
Purchase #7	$192.61	11.703%	$215.1511	$215.15	$215.15	$215.20
7 purchase totals =	$876.44		$954.4652	$954.46	$954.45	$954.50