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	$54.71	12.248%	$61.4109	$61.41	$61.40	$61.40
Purchase #2	$209.90	9.141%	$229.087	$229.09	$229.10	$229.10
Purchase #3	$214.37	4.149%	$223.2642	$223.26	$223.25	$223.30
Purchase #4	$240.89	12.272%	$270.452	$270.45	$270.45	$270.50
Purchase #5	$24.43	11.761%	$27.3032	$27.30	$27.30	$27.30
Purchase #6	$120.45	4.396%	$125.745	$125.75	$125.75	$125.70
Purchase #7	$199.62	11.256%	$222.0892	$222.09	$222.10	$222.10
7 purchase totals =	$1,064.37		$1,159.3515	$1,159.35	$1,159.35	$1,159.40