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	$29.28	10.396%	$32.3239	$32.32	$32.30	$32.30
Purchase #2	$92.45	9.601%	$101.3261	$101.33	$101.35	$101.30
Purchase #3	$134.87	7.405%	$144.8571	$144.86	$144.85	$144.90
Purchase #4	$113.95	9.468%	$124.7388	$124.74	$124.75	$124.70
Purchase #5	$147.34	5.759%	$155.8253	$155.83	$155.85	$155.80
Purchase #6	$71.80	11.560%	$80.1001	$80.10	$80.10	$80.10
Purchase #7	$74.91	11.834%	$83.7748	$83.77	$83.75	$83.80
7 purchase totals =	$664.60		$722.9461	$722.95	$722.95	$722.90