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	$73.34	13.776%	$83.4433	$83.44	$83.45	$83.40
Purchase #2	$143.50	12.125%	$160.8994	$160.90	$160.90	$160.90
Purchase #3	$162.48	3.472%	$168.1213	$168.12	$168.10	$168.10
Purchase #4	$68.49	5.143%	$72.0124	$72.01	$72.00	$72.00
Purchase #5	$158.84	7.689%	$171.0532	$171.05	$171.05	$171.10
Purchase #6	$162.38	8.146%	$175.6075	$175.61	$175.60	$175.60
Purchase #7	$224.67	12.425%	$252.5852	$252.59	$252.60	$252.60
7 purchase totals =	$993.70		$1,083.7223	$1,083.72	$1,083.70	$1,083.70