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	$71.85	13.325%	$81.424	$81.42	$81.40	$81.40
Purchase #2	$246.89	11.207%	$274.559	$274.56	$274.55	$274.60
Purchase #3	$113.36	3.801%	$117.6688	$117.67	$117.65	$117.70
Purchase #4	$33.31	3.827%	$34.5848	$34.58	$34.60	$34.60
Purchase #5	$229.36	11.221%	$255.0965	$255.10	$255.10	$255.10
Purchase #6	$123.26	13.485%	$139.8816	$139.88	$139.90	$139.90
Purchase #7	$156.36	9.485%	$171.1907	$171.19	$171.20	$171.20
7 purchase totals =	$974.39		$1,074.4054	$1,074.40	$1,074.40	$1,074.50