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	$89.48	13.128%	$101.2269	$101.23	$101.25	$101.20
Purchase #2	$229.76	4.559%	$240.2348	$240.23	$240.25	$240.20
Purchase #3	$54.70	13.253%	$61.9494	$61.95	$61.95	$61.90
Purchase #4	$155.62	10.784%	$172.4021	$172.40	$172.40	$172.40
Purchase #5	$44.69	13.629%	$50.7808	$50.78	$50.80	$50.80
Purchase #6	$249.73	10.853%	$276.8332	$276.83	$276.85	$276.80
Purchase #7	$220.54	13.367%	$250.0196	$250.02	$250.00	$250.00
7 purchase totals =	$1,044.52		$1,153.4468	$1,153.44	$1,153.50	$1,153.30