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	$62.65	13.701%	$71.2337	$71.23	$71.25	$71.20
Purchase #2	$40.38	8.238%	$43.7065	$43.71	$43.70	$43.70
Purchase #3	$107.72	5.603%	$113.7556	$113.76	$113.75	$113.80
Purchase #4	$39.90	8.181%	$43.1642	$43.16	$43.15	$43.20
Purchase #5	$33.31	4.604%	$34.8436	$34.84	$34.85	$34.80
Purchase #6	$210.81	11.330%	$234.6948	$234.69	$234.70	$234.70
Purchase #7	$142.95	11.342%	$159.1634	$159.16	$159.15	$159.20
7 purchase totals =	$637.72		$700.5618	$700.55	$700.55	$700.60