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	$208.94	4.291%	$217.9056	$217.91	$217.90	$217.90
Purchase #2	$202.77	11.535%	$226.1595	$226.16	$226.15	$226.20
Purchase #3	$101.43	4.338%	$105.83	$105.83	$105.85	$105.80
Purchase #4	$89.93	12.434%	$101.1119	$101.11	$101.10	$101.10
Purchase #5	$134.33	3.857%	$139.5111	$139.51	$139.50	$139.50
Purchase #6	$171.37	4.592%	$179.2393	$179.24	$179.25	$179.20
Purchase #7	$121.75	12.438%	$136.8933	$136.89	$136.90	$136.90
7 purchase totals =	$1,030.52		$1,106.6507	$1,106.65	$1,106.65	$1,106.60