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	$120.25	11.162%	$133.6723	$133.67	$133.65	$133.70
Purchase #2	$85.90	5.711%	$90.8057	$90.81	$90.80	$90.80
Purchase #3	$120.69	10.620%	$133.5073	$133.51	$133.50	$133.50
Purchase #4	$206.51	4.633%	$216.0776	$216.08	$216.10	$216.10
Purchase #5	$38.56	8.607%	$41.8789	$41.88	$41.90	$41.90
Purchase #6	$113.76	4.604%	$118.9975	$119.00	$119.00	$119.00
Purchase #7	$78.56	8.459%	$85.2054	$85.21	$85.20	$85.20
7 purchase totals =	$764.23		$820.1447	$820.16	$820.15	$820.20