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	$40.29	13.448%	$45.7082	$45.71	$45.70	$45.70
Purchase #2	$120.46	13.760%	$137.0353	$137.04	$137.05	$137.00
Purchase #3	$58.55	12.806%	$66.0479	$66.05	$66.05	$66.00
Purchase #4	$112.63	13.259%	$127.5636	$127.56	$127.55	$127.60
Purchase #5	$250.48	12.347%	$281.4068	$281.41	$281.40	$281.40
Purchase #6	$130.95	12.770%	$147.6723	$147.67	$147.65	$147.70
Purchase #7	$194.61	8.402%	$210.9611	$210.96	$210.95	$211.00
7 purchase totals =	$907.97		$1,016.3952	$1,016.40	$1,016.35	$1,016.40