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	$192.79	12.435%	$216.7634	$216.76	$216.75	$216.80
Purchase #2	$83.43	13.727%	$94.8824	$94.88	$94.90	$94.90
Purchase #3	$232.88	7.569%	$250.5067	$250.51	$250.50	$250.50
Purchase #4	$19.68	3.346%	$20.3385	$20.34	$20.35	$20.30
Purchase #5	$62.66	13.192%	$70.9261	$70.93	$70.95	$70.90
Purchase #6	$53.38	11.332%	$59.429	$59.43	$59.45	$59.40
Purchase #7	$80.60	13.474%	$91.46	$91.46	$91.45	$91.50
7 purchase totals =	$725.42		$804.3061	$804.31	$804.35	$804.30