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	$197.69	10.473%	$218.3941	$218.39	$218.40	$218.40
Purchase #2	$146.90	12.227%	$164.8615	$164.86	$164.85	$164.90
Purchase #3	$191.64	4.741%	$200.7257	$200.73	$200.75	$200.70
Purchase #4	$126.55	9.666%	$138.7823	$138.78	$138.80	$138.80
Purchase #5	$60.68	11.152%	$67.447	$67.45	$67.45	$67.40
Purchase #6	$180.41	6.255%	$191.6946	$191.69	$191.70	$191.70
Purchase #7	$227.82	11.760%	$254.6116	$254.61	$254.60	$254.60
7 purchase totals =	$1,131.69		$1,236.5168	$1,236.51	$1,236.55	$1,236.50