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	$153.38	11.521%	$171.0509	$171.05	$171.05	$171.10
Purchase #2	$93.94	6.304%	$99.862	$99.86	$99.85	$99.90
Purchase #3	$151.98	5.731%	$160.69	$160.69	$160.70	$160.70
Purchase #4	$173.99	4.643%	$182.0684	$182.07	$182.05	$182.10
Purchase #5	$247.79	13.761%	$281.8884	$281.89	$281.90	$281.90
Purchase #6	$237.48	8.816%	$258.4162	$258.42	$258.40	$258.40
Purchase #7	$77.73	13.803%	$88.4591	$88.46	$88.45	$88.50
7 purchase totals =	$1,136.29		$1,242.4350	$1,242.44	$1,242.40	$1,242.60