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	$222.94	6.763%	$238.0174	$238.02	$238.00	$238.00
Purchase #2	$50.46	10.603%	$55.8103	$55.81	$55.80	$55.80
Purchase #3	$246.49	3.274%	$254.5601	$254.56	$254.55	$254.60
Purchase #4	$170.43	12.621%	$191.94	$191.94	$191.95	$191.90
Purchase #5	$168.30	5.366%	$177.331	$177.33	$177.35	$177.30
Purchase #6	$95.72	5.211%	$100.708	$100.71	$100.70	$100.70
Purchase #7	$125.27	13.476%	$142.1514	$142.15	$142.15	$142.20
7 purchase totals =	$1,079.61		$1,160.5182	$1,160.52	$1,160.50	$1,160.50