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	$193.89	10.264%	$213.7909	$213.79	$213.80	$213.80
Purchase #2	$229.51	10.873%	$254.4646	$254.46	$254.45	$254.50
Purchase #3	$133.64	12.258%	$150.0216	$150.02	$150.00	$150.00
Purchase #4	$98.56	13.136%	$111.5068	$111.51	$111.50	$111.50
Purchase #5	$33.71	12.586%	$37.9527	$37.95	$37.95	$38.00
Purchase #6	$78.41	3.532%	$81.1794	$81.18	$81.20	$81.20
Purchase #7	$92.77	7.475%	$99.7046	$99.70	$99.70	$99.70
7 purchase totals =	$860.49		$948.6206	$948.61	$948.60	$948.70