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	$76.66	11.800%	$85.7059	$85.71	$85.70	$85.70
Purchase #2	$139.43	10.700%	$154.349	$154.35	$154.35	$154.30
Purchase #3	$124.76	5.714%	$131.8888	$131.89	$131.90	$131.90
Purchase #4	$22.62	13.442%	$25.6606	$25.66	$25.65	$25.70
Purchase #5	$206.69	3.674%	$214.2838	$214.28	$214.30	$214.30
Purchase #6	$80.83	7.254%	$86.6934	$86.69	$86.70	$86.70
Purchase #7	$141.53	5.180%	$148.8613	$148.86	$148.85	$148.90
7 purchase totals =	$792.52		$847.4428	$847.44	$847.45	$847.50