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	$192.60	12.688%	$217.0371	$217.04	$217.05	$217.00
Purchase #2	$176.90	13.360%	$200.5338	$200.53	$200.55	$200.50
Purchase #3	$195.60	13.288%	$221.5913	$221.59	$221.60	$221.60
Purchase #4	$167.70	6.520%	$178.634	$178.63	$178.65	$178.60
Purchase #5	$104.68	4.154%	$109.0284	$109.03	$109.05	$109.00
Purchase #6	$236.38	7.240%	$253.4939	$253.49	$253.50	$253.50
Purchase #7	$150.27	10.118%	$165.4743	$165.47	$165.45	$165.50
7 purchase totals =	$1,224.13		$1,345.7928	$1,345.78	$1,345.85	$1,345.70