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	$174.46	4.673%	$182.6125	$182.61	$182.60	$182.60
Purchase #2	$64.99	6.771%	$69.3905	$69.39	$69.40	$69.40
Purchase #3	$126.64	11.744%	$141.5126	$141.51	$141.50	$141.50
Purchase #4	$238.59	7.240%	$255.8639	$255.86	$255.85	$255.90
Purchase #5	$175.49	6.624%	$187.1145	$187.11	$187.10	$187.10
Purchase #6	$225.84	12.431%	$253.9142	$253.91	$253.90	$253.90
Purchase #7	$204.41	6.573%	$217.8459	$217.85	$217.85	$217.80
7 purchase totals =	$1,210.42		$1,308.2541	$1,308.24	$1,308.20	$1,308.20