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	$223.92	9.204%	$244.5296	$244.53	$244.55	$244.50
Purchase #2	$176.64	12.134%	$198.0735	$198.07	$198.05	$198.10
Purchase #3	$30.51	9.869%	$33.521	$33.52	$33.50	$33.50
Purchase #4	$91.70	8.457%	$99.4551	$99.46	$99.45	$99.50
Purchase #5	$127.89	9.823%	$140.4526	$140.45	$140.45	$140.50
Purchase #6	$107.60	6.276%	$114.353	$114.35	$114.35	$114.40
Purchase #7	$180.57	4.688%	$189.0351	$189.04	$189.05	$189.00
7 purchase totals =	$938.83		$1,019.4199	$1,019.42	$1,019.40	$1,019.50