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	$204.52	8.541%	$221.9881	$221.99	$222.00	$222.00
Purchase #2	$108.54	3.131%	$111.9384	$111.94	$111.95	$111.90
Purchase #3	$130.45	11.166%	$145.016	$145.02	$145.00	$145.00
Purchase #4	$125.54	11.440%	$139.9018	$139.90	$139.90	$139.90
Purchase #5	$232.57	9.469%	$254.5921	$254.59	$254.60	$254.60
Purchase #6	$216.54	13.409%	$245.5758	$245.58	$245.60	$245.60
Purchase #7	$114.36	12.229%	$128.3451	$128.35	$128.35	$128.30
7 purchase totals =	$1,132.52		$1,247.3573	$1,247.37	$1,247.40	$1,247.30