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	$31.36	6.459%	$33.3855	$33.39	$33.40	$33.40
Purchase #2	$78.90	7.747%	$85.0124	$85.01	$85.00	$85.00
Purchase #3	$233.52	9.850%	$256.5217	$256.52	$256.50	$256.50
Purchase #4	$240.74	9.565%	$263.7668	$263.77	$263.75	$263.80
Purchase #5	$93.28	12.644%	$105.0743	$105.07	$105.05	$105.10
Purchase #6	$210.33	3.485%	$217.66	$217.66	$217.65	$217.70
Purchase #7	$55.71	11.544%	$62.1412	$62.14	$62.15	$62.10
7 purchase totals =	$943.84		$1,023.5619	$1,023.56	$1,023.50	$1,023.60