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	$149.94	7.325%	$160.9231	$160.92	$160.90	$160.90
Purchase #2	$39.48	6.749%	$42.1445	$42.14	$42.15	$42.10
Purchase #3	$199.78	7.858%	$215.4787	$215.48	$215.50	$215.50
Purchase #4	$216.97	8.732%	$235.9158	$235.92	$235.90	$235.90
Purchase #5	$158.82	6.427%	$169.0274	$169.03	$169.05	$169.00
Purchase #6	$47.88	11.840%	$53.549	$53.55	$53.55	$53.50
Purchase #7	$162.95	5.859%	$172.4972	$172.50	$172.50	$172.50
7 purchase totals =	$975.82		$1,049.5357	$1,049.54	$1,049.55	$1,049.40