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	$168.27	11.764%	$188.0653	$188.07	$188.05	$188.10
Purchase #2	$236.67	12.167%	$265.4656	$265.47	$265.45	$265.50
Purchase #3	$189.89	5.657%	$200.6321	$200.63	$200.65	$200.60
Purchase #4	$214.41	3.128%	$221.1167	$221.12	$221.10	$221.10
Purchase #5	$89.84	13.693%	$102.1418	$102.14	$102.15	$102.10
Purchase #6	$75.29	13.861%	$85.7259	$85.73	$85.75	$85.70
Purchase #7	$241.60	13.872%	$275.1148	$275.11	$275.10	$275.10
7 purchase totals =	$1,215.97		$1,338.2622	$1,338.27	$1,338.25	$1,338.20