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	$147.75	8.582%	$160.4299	$160.43	$160.45	$160.40
Purchase #2	$200.41	4.632%	$209.693	$209.69	$209.70	$209.70
Purchase #3	$48.73	3.754%	$50.5593	$50.56	$50.55	$50.60
Purchase #4	$173.46	4.439%	$181.1599	$181.16	$181.15	$181.20
Purchase #5	$52.79	8.436%	$57.2434	$57.24	$57.25	$57.20
Purchase #6	$64.37	4.342%	$67.1649	$67.16	$67.15	$67.20
Purchase #7	$108.61	5.812%	$114.9224	$114.92	$114.90	$114.90
7 purchase totals =	$796.12		$841.1728	$841.16	$841.15	$841.20