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	$196.74	3.258%	$203.1498	$203.15	$203.15	$203.10
Purchase #2	$192.91	3.220%	$199.1217	$199.12	$199.10	$199.10
Purchase #3	$140.53	13.106%	$158.9479	$158.95	$158.95	$158.90
Purchase #4	$135.81	10.539%	$150.123	$150.12	$150.10	$150.10
Purchase #5	$170.94	5.809%	$180.8699	$180.87	$180.85	$180.90
Purchase #6	$99.47	11.178%	$110.5888	$110.59	$110.60	$110.60
Purchase #7	$151.88	13.340%	$172.1408	$172.14	$172.15	$172.10
7 purchase totals =	$1,088.28		$1,174.9419	$1,174.94	$1,174.90	$1,174.80