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	$150.43	4.814%	$157.6717	$157.67	$157.65	$157.70
Purchase #2	$46.28	13.411%	$52.4866	$52.49	$52.50	$52.50
Purchase #3	$175.90	7.178%	$188.5261	$188.53	$188.55	$188.50
Purchase #4	$65.87	11.802%	$73.644	$73.64	$73.65	$73.60
Purchase #5	$53.85	11.308%	$59.9394	$59.94	$59.95	$59.90
Purchase #6	$238.37	4.727%	$249.6377	$249.64	$249.65	$249.60
Purchase #7	$92.69	8.453%	$100.5251	$100.53	$100.55	$100.50
7 purchase totals =	$823.39		$882.4306	$882.44	$882.50	$882.30