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	$121.82	11.844%	$136.2484	$136.25	$136.25	$136.20
Purchase #2	$242.76	5.144%	$255.2476	$255.25	$255.25	$255.20
Purchase #3	$243.54	12.797%	$274.7058	$274.71	$274.70	$274.70
Purchase #4	$216.98	7.573%	$233.4119	$233.41	$233.40	$233.40
Purchase #5	$37.67	7.477%	$40.4866	$40.49	$40.50	$40.50
Purchase #6	$20.68	6.378%	$21.999	$22.00	$22.00	$22.00
Purchase #7	$137.80	10.631%	$152.4495	$152.45	$152.45	$152.40
7 purchase totals =	$1,021.25		$1,114.5488	$1,114.56	$1,114.55	$1,114.40