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	$132.27	6.766%	$141.2194	$141.22	$141.20	$141.20
Purchase #2	$170.61	11.795%	$190.7334	$190.73	$190.75	$190.70
Purchase #3	$169.62	12.212%	$190.334	$190.33	$190.35	$190.30
Purchase #4	$207.52	3.263%	$214.2914	$214.29	$214.30	$214.30
Purchase #5	$131.29	12.365%	$147.524	$147.52	$147.50	$147.50
Purchase #6	$50.50	3.115%	$52.0731	$52.07	$52.05	$52.10
Purchase #7	$165.46	6.187%	$175.697	$175.70	$175.70	$175.70
7 purchase totals =	$1,027.27		$1,111.8723	$1,111.86	$1,111.85	$1,111.80