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	$151.34	10.619%	$167.4108	$167.41	$167.40	$167.40
Purchase #2	$48.98	11.734%	$54.7273	$54.73	$54.75	$54.70
Purchase #3	$128.80	11.189%	$143.2114	$143.21	$143.20	$143.20
Purchase #4	$69.25	4.487%	$72.3572	$72.36	$72.35	$72.40
Purchase #5	$238.91	7.432%	$256.6658	$256.67	$256.65	$256.70
Purchase #6	$74.30	12.107%	$83.2955	$83.30	$83.30	$83.30
Purchase #7	$119.53	6.335%	$127.1022	$127.10	$127.10	$127.10
7 purchase totals =	$831.11		$904.7702	$904.78	$904.75	$904.80