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	$59.78	13.113%	$67.619	$67.62	$67.60	$67.60
Purchase #2	$32.58	3.357%	$33.6737	$33.67	$33.65	$33.70
Purchase #3	$245.96	12.438%	$276.5525	$276.55	$276.55	$276.60
Purchase #4	$27.35	3.627%	$28.342	$28.34	$28.35	$28.30
Purchase #5	$19.62	9.523%	$21.4884	$21.49	$21.50	$21.50
Purchase #6	$145.59	9.721%	$159.7428	$159.74	$159.75	$159.70
Purchase #7	$137.36	10.313%	$151.5259	$151.53	$151.55	$151.50
7 purchase totals =	$668.24		$738.9443	$738.94	$738.95	$738.90