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	$169.58	12.460%	$190.7097	$190.71	$190.70	$190.70
Purchase #2	$200.89	4.333%	$209.5946	$209.59	$209.60	$209.60
Purchase #3	$174.63	6.625%	$186.1992	$186.20	$186.20	$186.20
Purchase #4	$6.81	10.661%	$7.536	$7.54	$7.55	$7.50
Purchase #5	$223.66	10.691%	$247.5715	$247.57	$247.55	$247.60
Purchase #6	$130.75	5.109%	$137.43	$137.43	$137.45	$137.40
Purchase #7	$172.68	10.483%	$190.782	$190.78	$190.80	$190.80
7 purchase totals =	$1,079.00		$1,169.8230	$1,169.82	$1,169.85	$1,169.80