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	$111.42	12.613%	$125.4734	$125.47	$125.45	$125.50
Purchase #2	$176.61	7.816%	$190.4138	$190.41	$190.40	$190.40
Purchase #3	$131.43	11.555%	$146.6167	$146.62	$146.60	$146.60
Purchase #4	$106.99	3.718%	$110.9679	$110.97	$110.95	$111.00
Purchase #5	$238.37	11.660%	$266.1639	$266.16	$266.15	$266.20
Purchase #6	$84.46	8.343%	$91.5065	$91.51	$91.50	$91.50
Purchase #7	$174.73	3.838%	$181.4361	$181.44	$181.45	$181.40
7 purchase totals =	$1,024.01		$1,112.5783	$1,112.58	$1,112.50	$1,112.60