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	$94.28	11.761%	$105.3683	$105.37	$105.35	$105.40
Purchase #2	$242.75	6.626%	$258.8346	$258.83	$258.85	$258.80
Purchase #3	$135.29	6.148%	$143.6076	$143.61	$143.60	$143.60
Purchase #4	$100.41	10.681%	$111.1348	$111.13	$111.15	$111.10
Purchase #5	$31.82	7.199%	$34.1107	$34.11	$34.10	$34.10
Purchase #6	$234.47	5.767%	$247.9919	$247.99	$248.00	$248.00
Purchase #7	$110.64	9.841%	$121.5281	$121.53	$121.55	$121.50
7 purchase totals =	$949.66		$1,022.5760	$1,022.57	$1,022.60	$1,022.50