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	$53.27	12.545%	$59.9527	$59.95	$59.95	$60.00
Purchase #2	$159.91	7.269%	$171.5339	$171.53	$171.55	$171.50
Purchase #3	$185.27	13.442%	$210.174	$210.17	$210.15	$210.20
Purchase #4	$110.76	12.167%	$124.2362	$124.24	$124.25	$124.20
Purchase #5	$40.89	6.536%	$43.5626	$43.56	$43.55	$43.60
Purchase #6	$20.61	10.681%	$22.8114	$22.81	$22.80	$22.80
Purchase #7	$165.90	5.705%	$175.3646	$175.36	$175.35	$175.40
7 purchase totals =	$736.61		$807.6354	$807.62	$807.60	$807.70