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	$40.76	5.385%	$42.9549	$42.95	$42.95	$43.00
Purchase #2	$167.50	13.687%	$190.4257	$190.43	$190.45	$190.40
Purchase #3	$209.80	12.723%	$236.4929	$236.49	$236.50	$236.50
Purchase #4	$94.77	10.630%	$104.8441	$104.84	$104.85	$104.80
Purchase #5	$47.44	10.325%	$52.3382	$52.34	$52.35	$52.30
Purchase #6	$159.96	5.593%	$168.9066	$168.91	$168.90	$168.90
Purchase #7	$247.60	13.686%	$281.4865	$281.49	$281.50	$281.50
7 purchase totals =	$967.83		$1,077.4489	$1,077.45	$1,077.50	$1,077.40