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	$127.85	10.642%	$141.4558	$141.46	$141.45	$141.50
Purchase #2	$138.78	13.592%	$157.643	$157.64	$157.65	$157.60
Purchase #3	$133.31	9.858%	$146.4517	$146.45	$146.45	$146.50
Purchase #4	$188.51	4.239%	$196.5009	$196.50	$196.50	$196.50
Purchase #5	$144.58	6.844%	$154.4751	$154.48	$154.50	$154.50
Purchase #6	$172.36	8.559%	$187.1123	$187.11	$187.10	$187.10
Purchase #7	$196.85	10.512%	$217.5429	$217.54	$217.55	$217.50
7 purchase totals =	$1,102.24		$1,201.1817	$1,201.18	$1,201.20	$1,201.20