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	$61.29	4.821%	$64.2448	$64.24	$64.25	$64.20
Purchase #2	$185.72	12.819%	$209.5274	$209.53	$209.55	$209.50
Purchase #3	$223.89	8.291%	$242.4527	$242.45	$242.45	$242.50
Purchase #4	$211.86	6.152%	$224.8936	$224.89	$224.90	$224.90
Purchase #5	$137.28	11.836%	$153.5285	$153.53	$153.55	$153.50
Purchase #6	$194.31	4.539%	$203.1297	$203.13	$203.15	$203.10
Purchase #7	$225.39	4.616%	$235.794	$235.79	$235.80	$235.80
7 purchase totals =	$1,239.74		$1,333.5707	$1,333.56	$1,333.65	$1,333.50