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	$203.33	4.284%	$212.0407	$212.04	$212.05	$212.00
Purchase #2	$145.80	13.738%	$165.83	$165.83	$165.85	$165.80
Purchase #3	$97.93	12.209%	$109.8863	$109.89	$109.90	$109.90
Purchase #4	$32.45	10.160%	$35.7469	$35.75	$35.75	$35.70
Purchase #5	$28.69	13.430%	$32.5431	$32.54	$32.55	$32.50
Purchase #6	$11.68	5.619%	$12.3363	$12.34	$12.35	$12.30
Purchase #7	$176.42	11.119%	$196.0361	$196.04	$196.05	$196.00
7 purchase totals =	$696.30		$764.4194	$764.43	$764.50	$764.20