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	$108.85	9.833%	$119.5532	$119.55	$119.55	$119.60
Purchase #2	$223.25	8.762%	$242.8112	$242.81	$242.80	$242.80
Purchase #3	$28.43	3.378%	$29.3904	$29.39	$29.40	$29.40
Purchase #4	$64.32	11.689%	$71.8384	$71.84	$71.85	$71.80
Purchase #5	$48.88	10.805%	$54.1615	$54.16	$54.15	$54.20
Purchase #6	$229.49	5.389%	$241.8572	$241.86	$241.85	$241.90
Purchase #7	$238.43	8.430%	$258.5296	$258.53	$258.55	$258.50
7 purchase totals =	$941.65		$1,018.1415	$1,018.14	$1,018.15	$1,018.20