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	$47.72	13.655%	$54.2362	$54.24	$54.25	$54.20
Purchase #2	$90.89	9.868%	$99.859	$99.86	$99.85	$99.90
Purchase #3	$87.58	6.796%	$93.5319	$93.53	$93.55	$93.50
Purchase #4	$97.43	7.416%	$104.6554	$104.66	$104.65	$104.70
Purchase #5	$156.49	7.717%	$168.5663	$168.57	$168.55	$168.60
Purchase #6	$53.51	3.804%	$55.5455	$55.55	$55.55	$55.50
Purchase #7	$121.96	7.102%	$130.6216	$130.62	$130.60	$130.60
7 purchase totals =	$655.58		$707.0159	$707.03	$707.00	$707.00