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	$248.48	13.472%	$281.9552	$281.96	$281.95	$282.00
Purchase #2	$18.56	12.230%	$20.8299	$20.83	$20.85	$20.80
Purchase #3	$68.78	13.470%	$78.0447	$78.04	$78.05	$78.00
Purchase #4	$87.25	5.874%	$92.3751	$92.38	$92.40	$92.40
Purchase #5	$200.36	6.872%	$214.1287	$214.13	$214.15	$214.10
Purchase #6	$212.59	6.473%	$226.351	$226.35	$226.35	$226.40
Purchase #7	$194.50	3.191%	$200.7065	$200.71	$200.70	$200.70
7 purchase totals =	$1,030.52		$1,114.3911	$1,114.40	$1,114.45	$1,114.40