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	$162.51	3.244%	$167.7818	$167.78	$167.80	$167.80
Purchase #2	$44.84	5.824%	$47.4515	$47.45	$47.45	$47.50
Purchase #3	$127.92	12.854%	$144.3628	$144.36	$144.35	$144.40
Purchase #4	$152.70	8.260%	$165.313	$165.31	$165.30	$165.30
Purchase #5	$111.76	11.779%	$124.9242	$124.92	$124.90	$124.90
Purchase #6	$116.93	11.587%	$130.4787	$130.48	$130.50	$130.50
Purchase #7	$202.39	11.625%	$225.9178	$225.92	$225.90	$225.90
7 purchase totals =	$919.05		$1,006.2298	$1,006.22	$1,006.20	$1,006.30