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	$182.59	7.607%	$196.4796	$196.48	$196.50	$196.50
Purchase #2	$221.44	7.593%	$238.2539	$238.25	$238.25	$238.30
Purchase #3	$104.55	11.458%	$116.5293	$116.53	$116.55	$116.50
Purchase #4	$75.45	4.612%	$78.9298	$78.93	$78.95	$78.90
Purchase #5	$5.85	13.442%	$6.6364	$6.64	$6.65	$6.60
Purchase #6	$163.56	7.513%	$175.8483	$175.85	$175.85	$175.80
Purchase #7	$137.59	5.221%	$144.7736	$144.77	$144.75	$144.80
7 purchase totals =	$891.03		$957.4509	$957.45	$957.50	$957.40