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	$64.82	13.302%	$73.4424	$73.44	$73.45	$73.40
Purchase #2	$84.59	4.248%	$88.1834	$88.18	$88.20	$88.20
Purchase #3	$84.55	6.517%	$90.0601	$90.06	$90.05	$90.10
Purchase #4	$208.33	4.843%	$218.4194	$218.42	$218.40	$218.40
Purchase #5	$242.60	9.437%	$265.4942	$265.49	$265.50	$265.50
Purchase #6	$139.73	9.203%	$152.5894	$152.59	$152.60	$152.60
Purchase #7	$139.63	13.640%	$158.6755	$158.68	$158.70	$158.70
7 purchase totals =	$964.25		$1,046.8644	$1,046.86	$1,046.90	$1,046.90