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	$71.75	13.431%	$81.3867	$81.39	$81.40	$81.40
Purchase #2	$245.32	12.415%	$275.7765	$275.78	$275.80	$275.80
Purchase #3	$245.29	4.241%	$255.6927	$255.69	$255.70	$255.70
Purchase #4	$165.26	9.268%	$180.5763	$180.58	$180.60	$180.60
Purchase #5	$80.61	13.652%	$91.6149	$91.61	$91.60	$91.60
Purchase #6	$120.40	6.708%	$128.4764	$128.48	$128.50	$128.50
Purchase #7	$213.41	8.194%	$230.8968	$230.90	$230.90	$230.90
7 purchase totals =	$1,142.04		$1,244.4203	$1,244.43	$1,244.50	$1,244.50