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	$220.31	7.525%	$236.8883	$236.89	$236.90	$236.90
Purchase #2	$240.35	6.188%	$255.2229	$255.22	$255.20	$255.20
Purchase #3	$22.54	10.610%	$24.9315	$24.93	$24.95	$24.90
Purchase #4	$130.98	4.338%	$136.6619	$136.66	$136.65	$136.70
Purchase #5	$166.41	13.297%	$188.5375	$188.54	$188.55	$188.50
Purchase #6	$96.91	9.352%	$105.973	$105.97	$105.95	$106.00
Purchase #7	$130.32	11.102%	$144.7881	$144.79	$144.80	$144.80
7 purchase totals =	$1,007.82		$1,093.0032	$1,093.00	$1,093.00	$1,093.00