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	$208.30	4.379%	$217.4215	$217.42	$217.40	$217.40
Purchase #2	$38.43	4.130%	$40.0172	$40.02	$40.00	$40.00
Purchase #3	$100.66	4.107%	$104.7941	$104.79	$104.80	$104.80
Purchase #4	$121.51	7.148%	$130.1955	$130.20	$130.20	$130.20
Purchase #5	$159.32	5.788%	$168.5414	$168.54	$168.55	$168.50
Purchase #6	$6.28	7.278%	$6.7371	$6.74	$6.75	$6.70
Purchase #7	$123.37	4.469%	$128.8834	$128.88	$128.90	$128.90
7 purchase totals =	$757.87		$796.5902	$796.59	$796.60	$796.50