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	$177.25	6.669%	$189.0708	$189.07	$189.05	$189.10
Purchase #2	$67.97	12.204%	$76.2651	$76.27	$76.25	$76.30
Purchase #3	$213.64	4.316%	$222.8607	$222.86	$222.85	$222.90
Purchase #4	$159.57	3.457%	$165.0863	$165.09	$165.10	$165.10
Purchase #5	$143.33	6.503%	$152.6507	$152.65	$152.65	$152.70
Purchase #6	$65.36	9.423%	$71.5189	$71.52	$71.50	$71.50
Purchase #7	$196.33	4.126%	$204.4306	$204.43	$204.45	$204.40
7 purchase totals =	$1,023.45		$1,081.8831	$1,081.89	$1,081.85	$1,082.00