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	$64.52	3.303%	$66.6511	$66.65	$66.65	$66.70
Purchase #2	$241.70	6.281%	$256.8812	$256.88	$256.90	$256.90
Purchase #3	$10.73	13.458%	$12.174	$12.17	$12.15	$12.20
Purchase #4	$161.60	4.731%	$169.2453	$169.25	$169.25	$169.20
Purchase #5	$178.26	10.297%	$196.6154	$196.62	$196.60	$196.60
Purchase #6	$141.98	5.803%	$150.2191	$150.22	$150.20	$150.20
Purchase #7	$212.41	13.148%	$240.3377	$240.34	$240.35	$240.30
7 purchase totals =	$1,011.20		$1,092.1238	$1,092.13	$1,092.10	$1,092.10