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	$104.74	6.106%	$111.1354	$111.14	$111.15	$111.10
Purchase #2	$25.34	10.569%	$28.0182	$28.02	$28.00	$28.00
Purchase #3	$179.43	12.873%	$202.528	$202.53	$202.55	$202.50
Purchase #4	$142.83	3.604%	$147.9776	$147.98	$148.00	$148.00
Purchase #5	$199.44	8.374%	$216.1411	$216.14	$216.15	$216.10
Purchase #6	$100.56	10.447%	$111.0655	$111.07	$111.05	$111.10
Purchase #7	$75.78	4.705%	$79.3454	$79.35	$79.35	$79.30
7 purchase totals =	$828.12		$896.2112	$896.23	$896.25	$896.10