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	$154.53	3.362%	$159.7253	$159.73	$159.75	$159.70
Purchase #2	$126.65	13.106%	$143.2487	$143.25	$143.25	$143.20
Purchase #3	$159.54	12.767%	$179.9085	$179.91	$179.90	$179.90
Purchase #4	$64.97	13.779%	$73.9222	$73.92	$73.90	$73.90
Purchase #5	$236.40	3.753%	$245.2721	$245.27	$245.25	$245.30
Purchase #6	$132.74	13.677%	$150.8948	$150.89	$150.90	$150.90
Purchase #7	$124.69	6.762%	$133.1215	$133.12	$133.10	$133.10
7 purchase totals =	$999.52		$1,086.0931	$1,086.09	$1,086.05	$1,086.00