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	$238.77	6.852%	$255.1305	$255.13	$255.15	$255.10
Purchase #2	$66.36	6.629%	$70.759	$70.76	$70.75	$70.80
Purchase #3	$129.51	5.692%	$136.8817	$136.88	$136.90	$136.90
Purchase #4	$140.29	9.575%	$153.7228	$153.72	$153.70	$153.70
Purchase #5	$217.27	6.373%	$231.1166	$231.12	$231.10	$231.10
Purchase #6	$6.80	3.484%	$7.0369	$7.04	$7.05	$7.00
Purchase #7	$213.50	13.495%	$242.3118	$242.31	$242.30	$242.30
7 purchase totals =	$1,012.50		$1,096.9593	$1,096.96	$1,096.95	$1,096.90