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	$94.41	9.580%	$103.4545	$103.45	$103.45	$103.50
Purchase #2	$104.47	13.512%	$118.586	$118.59	$118.60	$118.60
Purchase #3	$83.34	4.263%	$86.8928	$86.89	$86.90	$86.90
Purchase #4	$71.26	10.114%	$78.4672	$78.47	$78.45	$78.50
Purchase #5	$215.25	7.122%	$230.5801	$230.58	$230.60	$230.60
Purchase #6	$98.76	11.448%	$110.066	$110.07	$110.05	$110.10
Purchase #7	$38.45	9.596%	$42.1397	$42.14	$42.15	$42.10
7 purchase totals =	$705.94		$770.1863	$770.19	$770.20	$770.30