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	$65.29	12.252%	$73.2893	$73.29	$73.30	$73.30
Purchase #2	$137.87	10.461%	$152.2926	$152.29	$152.30	$152.30
Purchase #3	$118.42	4.140%	$123.3226	$123.32	$123.30	$123.30
Purchase #4	$180.37	6.231%	$191.6089	$191.61	$191.60	$191.60
Purchase #5	$40.73	4.327%	$42.4924	$42.49	$42.50	$42.50
Purchase #6	$90.94	10.179%	$100.1968	$100.20	$100.20	$100.20
Purchase #7	$200.90	11.580%	$224.1642	$224.16	$224.15	$224.20
7 purchase totals =	$834.52		$907.3668	$907.36	$907.35	$907.40