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	$242.49	4.867%	$254.292	$254.29	$254.30	$254.30
Purchase #2	$137.27	10.106%	$151.1425	$151.14	$151.15	$151.10
Purchase #3	$204.35	10.311%	$225.4205	$225.42	$225.40	$225.40
Purchase #4	$200.35	9.392%	$219.1669	$219.17	$219.15	$219.20
Purchase #5	$221.32	8.661%	$240.4885	$240.49	$240.50	$240.50
Purchase #6	$178.41	7.336%	$191.4982	$191.50	$191.50	$191.50
Purchase #7	$159.71	12.394%	$179.5045	$179.50	$179.50	$179.50
7 purchase totals =	$1,343.90		$1,461.5131	$1,461.51	$1,461.50	$1,461.50