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	$174.80	12.263%	$196.2357	$196.24	$196.25	$196.20
Purchase #2	$28.48	7.582%	$30.6394	$30.64	$30.65	$30.60
Purchase #3	$65.46	10.726%	$72.4812	$72.48	$72.50	$72.50
Purchase #4	$22.94	8.615%	$24.9163	$24.92	$24.90	$24.90
Purchase #5	$152.82	12.849%	$172.4558	$172.46	$172.45	$172.50
Purchase #6	$160.31	3.230%	$165.488	$165.49	$165.50	$165.50
Purchase #7	$78.77	12.257%	$88.4248	$88.42	$88.40	$88.40
7 purchase totals =	$683.58		$750.6412	$750.65	$750.65	$750.60