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	$40.34	8.295%	$43.6862	$43.69	$43.70	$43.70
Purchase #2	$144.53	5.672%	$152.7277	$152.73	$152.75	$152.70
Purchase #3	$10.38	13.114%	$11.7412	$11.74	$11.75	$11.70
Purchase #4	$62.83	3.620%	$65.1044	$65.10	$65.10	$65.10
Purchase #5	$70.27	11.537%	$78.377	$78.38	$78.40	$78.40
Purchase #6	$152.43	12.476%	$171.4472	$171.45	$171.45	$171.40
Purchase #7	$235.98	6.517%	$251.3588	$251.36	$251.35	$251.40
7 purchase totals =	$716.76		$774.4425	$774.45	$774.50	$774.40