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	$165.56	6.796%	$176.8115	$176.81	$176.80	$176.80
Purchase #2	$247.25	6.497%	$263.3138	$263.31	$263.30	$263.30
Purchase #3	$84.83	12.630%	$95.544	$95.54	$95.55	$95.50
Purchase #4	$250.81	13.771%	$285.349	$285.35	$285.35	$285.30
Purchase #5	$99.90	11.817%	$111.7052	$111.71	$111.70	$111.70
Purchase #6	$57.31	7.481%	$61.5974	$61.60	$61.60	$61.60
Purchase #7	$153.97	5.823%	$162.9357	$162.94	$162.95	$162.90
7 purchase totals =	$1,059.63		$1,157.2566	$1,157.26	$1,157.25	$1,157.10