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	$62.25	12.296%	$69.9043	$69.90	$69.90	$69.90
Purchase #2	$242.64	5.435%	$255.8275	$255.83	$255.85	$255.80
Purchase #3	$128.35	11.208%	$142.7355	$142.74	$142.75	$142.70
Purchase #4	$233.63	12.563%	$262.9809	$262.98	$263.00	$263.00
Purchase #5	$73.78	3.860%	$76.6279	$76.63	$76.65	$76.60
Purchase #6	$222.41	11.106%	$247.1109	$247.11	$247.10	$247.10
Purchase #7	$37.56	12.685%	$42.3245	$42.32	$42.30	$42.30
7 purchase totals =	$1,000.62		$1,097.5115	$1,097.51	$1,097.55	$1,097.40