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	$206.43	4.870%	$216.4831	$216.48	$216.50	$216.50
Purchase #2	$114.47	8.589%	$124.3018	$124.30	$124.30	$124.30
Purchase #3	$189.72	12.796%	$213.9966	$214.00	$214.00	$214.00
Purchase #4	$40.49	12.462%	$45.5359	$45.54	$45.55	$45.50
Purchase #5	$218.26	13.831%	$248.4475	$248.45	$248.45	$248.40
Purchase #6	$149.32	11.815%	$166.9622	$166.96	$166.95	$167.00
Purchase #7	$111.72	13.377%	$126.6648	$126.66	$126.65	$126.70
7 purchase totals =	$1,030.41		$1,142.3919	$1,142.39	$1,142.40	$1,142.40