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	$219.48	8.736%	$238.6538	$238.65	$238.65	$238.70
Purchase #2	$234.46	13.161%	$265.3173	$265.32	$265.30	$265.30
Purchase #3	$88.68	12.207%	$99.5052	$99.51	$99.50	$99.50
Purchase #4	$41.43	3.658%	$42.9455	$42.95	$42.95	$42.90
Purchase #5	$160.51	11.374%	$178.7664	$178.77	$178.75	$178.80
Purchase #6	$232.86	4.409%	$243.1268	$243.13	$243.15	$243.10
Purchase #7	$66.46	10.165%	$73.2157	$73.22	$73.20	$73.20
7 purchase totals =	$1,043.88		$1,141.5307	$1,141.55	$1,141.50	$1,141.50