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	$41.54	9.738%	$45.5852	$45.59	$45.60	$45.60
Purchase #2	$246.40	6.479%	$262.3643	$262.36	$262.35	$262.40
Purchase #3	$37.65	6.698%	$40.1718	$40.17	$40.15	$40.20
Purchase #4	$53.96	3.278%	$55.7288	$55.73	$55.75	$55.70
Purchase #5	$198.83	5.277%	$209.3223	$209.32	$209.30	$209.30
Purchase #6	$250.36	6.382%	$266.338	$266.34	$266.35	$266.30
Purchase #7	$221.31	13.388%	$250.939	$250.94	$250.95	$250.90
7 purchase totals =	$1,050.05		$1,130.4494	$1,130.45	$1,130.45	$1,130.40