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	$32.47	4.710%	$33.9993	$34.00	$34.00	$34.00
Purchase #2	$114.72	13.666%	$130.3976	$130.40	$130.40	$130.40
Purchase #3	$32.70	11.717%	$36.5315	$36.53	$36.55	$36.50
Purchase #4	$202.44	9.437%	$221.5443	$221.54	$221.55	$221.50
Purchase #5	$42.67	7.541%	$45.8877	$45.89	$45.90	$45.90
Purchase #6	$53.47	4.772%	$56.0216	$56.02	$56.00	$56.00
Purchase #7	$185.56	12.382%	$208.536	$208.54	$208.55	$208.50
7 purchase totals =	$664.03		$732.9180	$732.92	$732.95	$732.80