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	$209.61	10.223%	$231.0384	$231.04	$231.05	$231.00
Purchase #2	$235.25	8.290%	$254.7522	$254.75	$254.75	$254.80
Purchase #3	$120.31	5.721%	$127.1929	$127.19	$127.20	$127.20
Purchase #4	$132.89	12.827%	$149.9358	$149.94	$149.95	$149.90
Purchase #5	$209.30	7.626%	$225.2612	$225.26	$225.25	$225.30
Purchase #6	$159.48	12.800%	$179.8934	$179.89	$179.90	$179.90
Purchase #7	$82.90	5.445%	$87.4139	$87.41	$87.40	$87.40
7 purchase totals =	$1,149.74		$1,255.4878	$1,255.48	$1,255.50	$1,255.50