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	$193.81	3.542%	$200.6748	$200.67	$200.65	$200.70
Purchase #2	$188.29	10.632%	$208.309	$208.31	$208.30	$208.30
Purchase #3	$94.69	4.847%	$99.2796	$99.28	$99.30	$99.30
Purchase #4	$129.61	5.487%	$136.7217	$136.72	$136.70	$136.70
Purchase #5	$216.71	10.199%	$238.8123	$238.81	$238.80	$238.80
Purchase #6	$225.66	6.457%	$240.2309	$240.23	$240.25	$240.20
Purchase #7	$123.25	7.697%	$132.7366	$132.74	$132.75	$132.70
7 purchase totals =	$1,172.02		$1,256.7649	$1,256.76	$1,256.75	$1,256.70