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	$182.82	8.358%	$198.1001	$198.10	$198.10	$198.10
Purchase #2	$59.27	9.391%	$64.836	$64.84	$64.85	$64.80
Purchase #3	$151.60	8.846%	$165.0105	$165.01	$165.00	$165.00
Purchase #4	$167.45	11.147%	$186.1157	$186.12	$186.10	$186.10
Purchase #5	$137.34	9.682%	$150.6373	$150.64	$150.65	$150.60
Purchase #6	$205.59	7.579%	$221.1717	$221.17	$221.15	$221.20
Purchase #7	$140.99	10.262%	$155.4584	$155.46	$155.45	$155.50
7 purchase totals =	$1,045.06		$1,141.3297	$1,141.34	$1,141.30	$1,141.30