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	$86.68	7.874%	$93.5052	$93.51	$93.50	$93.50
Purchase #2	$84.56	13.534%	$96.0044	$96.00	$96.00	$96.00
Purchase #3	$193.41	13.468%	$219.4585	$219.46	$219.45	$219.50
Purchase #4	$190.63	5.340%	$200.8096	$200.81	$200.80	$200.80
Purchase #5	$139.53	13.461%	$158.3121	$158.31	$158.30	$158.30
Purchase #6	$91.52	9.812%	$100.4999	$100.50	$100.50	$100.50
Purchase #7	$11.88	8.718%	$12.9157	$12.92	$12.90	$12.90
7 purchase totals =	$798.21		$881.5054	$881.51	$881.45	$881.50