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	$232.62	13.558%	$264.1586	$264.16	$264.15	$264.20
Purchase #2	$124.77	12.818%	$140.763	$140.76	$140.75	$140.80
Purchase #3	$212.89	11.307%	$236.9615	$236.96	$236.95	$237.00
Purchase #4	$10.74	3.665%	$11.1336	$11.13	$11.15	$11.10
Purchase #5	$181.69	8.127%	$196.4559	$196.46	$196.45	$196.50
Purchase #6	$221.87	5.855%	$234.8605	$234.86	$234.85	$234.90
Purchase #7	$57.77	5.209%	$60.7792	$60.78	$60.80	$60.80
7 purchase totals =	$1,042.35		$1,145.1123	$1,145.11	$1,145.10	$1,145.30