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	$104.65	8.504%	$113.5494	$113.55	$113.55	$113.50
Purchase #2	$196.83	13.247%	$222.9041	$222.90	$222.90	$222.90
Purchase #3	$70.86	7.496%	$76.1717	$76.17	$76.15	$76.20
Purchase #4	$126.54	5.762%	$133.8312	$133.83	$133.85	$133.80
Purchase #5	$58.56	5.760%	$61.9331	$61.93	$61.95	$61.90
Purchase #6	$71.30	7.143%	$76.393	$76.39	$76.40	$76.40
Purchase #7	$115.91	8.504%	$125.767	$125.77	$125.75	$125.80
7 purchase totals =	$744.65		$810.5495	$810.54	$810.55	$810.50