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	$82.93	11.111%	$92.1444	$92.14	$92.15	$92.10
Purchase #2	$54.47	12.186%	$61.1077	$61.11	$61.10	$61.10
Purchase #3	$159.27	12.808%	$179.6693	$179.67	$179.65	$179.70
Purchase #4	$230.37	13.571%	$261.6335	$261.63	$261.65	$261.60
Purchase #5	$72.37	13.195%	$81.9192	$81.92	$81.90	$81.90
Purchase #6	$74.42	12.676%	$83.8535	$83.85	$83.85	$83.90
Purchase #7	$235.70	3.629%	$244.2536	$244.25	$244.25	$244.30
7 purchase totals =	$909.53		$1,004.5812	$1,004.57	$1,004.55	$1,004.60