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	$243.97	9.734%	$267.718	$267.72	$267.70	$267.70
Purchase #2	$225.72	13.275%	$255.6843	$255.68	$255.70	$255.70
Purchase #3	$201.85	11.749%	$225.5654	$225.57	$225.55	$225.60
Purchase #4	$148.40	12.344%	$166.7185	$166.72	$166.70	$166.70
Purchase #5	$153.57	9.581%	$168.2835	$168.28	$168.30	$168.30
Purchase #6	$165.77	8.193%	$179.3515	$179.35	$179.35	$179.40
Purchase #7	$88.40	13.858%	$100.6505	$100.65	$100.65	$100.70
7 purchase totals =	$1,227.68		$1,363.9717	$1,363.97	$1,363.95	$1,364.10