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	$146.32	3.517%	$151.4661	$151.47	$151.45	$151.50
Purchase #2	$91.69	9.589%	$100.4822	$100.48	$100.50	$100.50
Purchase #3	$167.90	12.865%	$189.5003	$189.50	$189.50	$189.50
Purchase #4	$223.86	7.331%	$240.2712	$240.27	$240.25	$240.30
Purchase #5	$62.94	3.472%	$65.1253	$65.13	$65.15	$65.10
Purchase #6	$188.63	4.682%	$197.4617	$197.46	$197.45	$197.50
Purchase #7	$215.39	7.145%	$230.7796	$230.78	$230.80	$230.80
7 purchase totals =	$1,096.73		$1,175.0864	$1,175.09	$1,175.10	$1,175.20