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	$126.59	7.123%	$135.607	$135.61	$135.60	$135.60
Purchase #2	$71.29	8.586%	$77.411	$77.41	$77.40	$77.40
Purchase #3	$153.28	6.249%	$162.8585	$162.86	$162.85	$162.90
Purchase #4	$72.58	6.149%	$77.0429	$77.04	$77.05	$77.00
Purchase #5	$65.90	9.132%	$71.918	$71.92	$71.90	$71.90
Purchase #6	$84.61	6.153%	$89.8161	$89.82	$89.80	$89.80
Purchase #7	$77.52	9.829%	$85.1394	$85.14	$85.15	$85.10
7 purchase totals =	$651.77		$699.7929	$699.80	$699.75	$699.70