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	$152.30	13.497%	$172.8559	$172.86	$172.85	$172.90
Purchase #2	$113.93	10.562%	$125.9633	$125.96	$125.95	$126.00
Purchase #3	$10.46	3.767%	$10.854	$10.85	$10.85	$10.90
Purchase #4	$247.34	3.753%	$256.6227	$256.62	$256.60	$256.60
Purchase #5	$85.56	3.385%	$88.4562	$88.46	$88.45	$88.50
Purchase #6	$169.93	13.643%	$193.1135	$193.11	$193.10	$193.10
Purchase #7	$89.97	4.798%	$94.2868	$94.29	$94.30	$94.30
7 purchase totals =	$869.49		$942.1524	$942.15	$942.10	$942.30