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	$115.82	13.692%	$131.6781	$131.68	$131.70	$131.70
Purchase #2	$223.87	4.341%	$233.5882	$233.59	$233.60	$233.60
Purchase #3	$50.73	10.167%	$55.8877	$55.89	$55.90	$55.90
Purchase #4	$217.82	5.150%	$229.0377	$229.04	$229.05	$229.00
Purchase #5	$221.86	12.675%	$249.9808	$249.98	$250.00	$250.00
Purchase #6	$187.87	9.738%	$206.1648	$206.16	$206.15	$206.20
Purchase #7	$45.36	10.802%	$50.2598	$50.26	$50.25	$50.30
7 purchase totals =	$1,063.33		$1,156.5971	$1,156.60	$1,156.65	$1,156.70