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	$34.26	10.382%	$37.8169	$37.82	$37.80	$37.80
Purchase #2	$9.98	7.553%	$10.7338	$10.73	$10.75	$10.70
Purchase #3	$67.63	7.689%	$72.8301	$72.83	$72.85	$72.80
Purchase #4	$247.85	3.350%	$256.153	$256.15	$256.15	$256.20
Purchase #5	$139.34	9.127%	$152.0576	$152.06	$152.05	$152.10
Purchase #6	$219.77	12.516%	$247.2764	$247.28	$247.30	$247.30
Purchase #7	$115.68	13.528%	$131.3292	$131.33	$131.35	$131.30
7 purchase totals =	$834.51		$908.1970	$908.20	$908.25	$908.20