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	$181.93	11.485%	$202.8247	$202.82	$202.80	$202.80
Purchase #2	$167.27	13.808%	$190.3666	$190.37	$190.35	$190.40
Purchase #3	$34.83	13.356%	$39.4819	$39.48	$39.50	$39.50
Purchase #4	$67.29	6.388%	$71.5885	$71.59	$71.60	$71.60
Purchase #5	$99.93	3.139%	$103.0668	$103.07	$103.05	$103.10
Purchase #6	$98.60	12.103%	$110.5336	$110.53	$110.55	$110.50
Purchase #7	$32.42	4.442%	$33.8601	$33.86	$33.85	$33.90
7 purchase totals =	$682.27		$751.7222	$751.72	$751.70	$751.80