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	$211.94	8.119%	$229.1474	$229.15	$229.15	$229.10
Purchase #2	$107.32	13.138%	$121.4197	$121.42	$121.40	$121.40
Purchase #3	$188.74	5.387%	$198.9074	$198.91	$198.90	$198.90
Purchase #4	$168.43	13.183%	$190.6341	$190.63	$190.65	$190.60
Purchase #5	$129.53	8.640%	$140.7214	$140.72	$140.70	$140.70
Purchase #6	$134.82	5.490%	$142.2216	$142.22	$142.20	$142.20
Purchase #7	$87.94	3.388%	$90.9194	$90.92	$90.90	$90.90
7 purchase totals =	$1,028.72		$1,113.9710	$1,113.97	$1,113.90	$1,113.80