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	$66.34	7.108%	$71.0554	$71.06	$71.05	$71.10
Purchase #2	$247.90	6.286%	$263.483	$263.48	$263.50	$263.50
Purchase #3	$37.31	5.711%	$39.4408	$39.44	$39.45	$39.40
Purchase #4	$214.87	10.828%	$238.1361	$238.14	$238.15	$238.10
Purchase #5	$146.39	10.259%	$161.4082	$161.41	$161.40	$161.40
Purchase #6	$246.34	4.843%	$258.2702	$258.27	$258.25	$258.30
Purchase #7	$24.61	13.421%	$27.9129	$27.91	$27.90	$27.90
7 purchase totals =	$983.76		$1,059.7066	$1,059.71	$1,059.70	$1,059.70