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	$186.82	11.591%	$208.4743	$208.47	$208.45	$208.50
Purchase #2	$235.63	4.160%	$245.4322	$245.43	$245.45	$245.40
Purchase #3	$236.42	5.868%	$250.2931	$250.29	$250.30	$250.30
Purchase #4	$188.49	5.187%	$198.267	$198.27	$198.25	$198.30
Purchase #5	$137.76	7.224%	$147.7118	$147.71	$147.70	$147.70
Purchase #6	$72.92	7.647%	$78.4962	$78.50	$78.50	$78.50
Purchase #7	$67.86	12.796%	$76.5434	$76.54	$76.55	$76.50
7 purchase totals =	$1,125.90		$1,205.2180	$1,205.21	$1,205.20	$1,205.20