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	$108.26	13.733%	$123.1273	$123.13	$123.15	$123.10
Purchase #2	$83.37	4.427%	$87.0608	$87.06	$87.05	$87.10
Purchase #3	$72.46	4.676%	$75.8482	$75.85	$75.85	$75.80
Purchase #4	$53.69	10.611%	$59.387	$59.39	$59.40	$59.40
Purchase #5	$73.31	7.201%	$78.5891	$78.59	$78.60	$78.60
Purchase #6	$121.94	7.757%	$131.3989	$131.40	$131.40	$131.40
Purchase #7	$68.73	10.621%	$76.0298	$76.03	$76.05	$76.00
7 purchase totals =	$581.76		$631.4411	$631.45	$631.50	$631.40