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	$131.73	7.619%	$141.7665	$141.77	$141.75	$141.80
Purchase #2	$31.70	3.658%	$32.8596	$32.86	$32.85	$32.90
Purchase #3	$232.63	4.515%	$243.1332	$243.13	$243.15	$243.10
Purchase #4	$101.83	3.221%	$105.1099	$105.11	$105.10	$105.10
Purchase #5	$139.88	4.855%	$146.6712	$146.67	$146.65	$146.70
Purchase #6	$71.74	8.121%	$77.566	$77.57	$77.55	$77.60
Purchase #7	$116.78	3.547%	$120.9222	$120.92	$120.90	$120.90
7 purchase totals =	$826.29		$868.0286	$868.03	$867.95	$868.10