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	$162.95	9.499%	$178.4286	$178.43	$178.45	$178.40
Purchase #2	$138.33	7.139%	$148.2054	$148.21	$148.20	$148.20
Purchase #3	$71.57	8.502%	$77.6549	$77.65	$77.65	$77.70
Purchase #4	$166.71	10.609%	$184.3963	$184.40	$184.40	$184.40
Purchase #5	$94.78	12.825%	$106.9355	$106.94	$106.95	$106.90
Purchase #6	$99.49	6.429%	$105.8862	$105.89	$105.90	$105.90
Purchase #7	$100.86	12.150%	$113.1145	$113.11	$113.10	$113.10
7 purchase totals =	$834.69		$914.6214	$914.63	$914.65	$914.60