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	$40.54	3.234%	$41.8511	$41.85	$41.85	$41.90
Purchase #2	$13.53	11.189%	$15.0439	$15.04	$15.05	$15.00
Purchase #3	$226.52	13.790%	$257.7571	$257.76	$257.75	$257.80
Purchase #4	$71.46	3.775%	$74.1576	$74.16	$74.15	$74.20
Purchase #5	$39.39	6.819%	$42.076	$42.08	$42.10	$42.10
Purchase #6	$225.86	6.664%	$240.9113	$240.91	$240.90	$240.90
Purchase #7	$190.25	5.501%	$200.7157	$200.72	$200.70	$200.70
7 purchase totals =	$807.55		$872.5127	$872.52	$872.50	$872.60