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	$100.70	3.149%	$103.871	$103.87	$103.85	$103.90
Purchase #2	$50.93	5.230%	$53.5936	$53.59	$53.60	$53.60
Purchase #3	$28.59	10.385%	$31.5591	$31.56	$31.55	$31.60
Purchase #4	$250.71	11.115%	$278.5764	$278.58	$278.60	$278.60
Purchase #5	$154.25	3.405%	$159.5022	$159.50	$159.50	$159.50
Purchase #6	$83.98	12.295%	$94.3053	$94.31	$94.30	$94.30
Purchase #7	$247.60	9.787%	$271.8326	$271.83	$271.85	$271.80
7 purchase totals =	$916.76		$993.2402	$993.24	$993.25	$993.30