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	$113.25	5.464%	$119.438	$119.44	$119.45	$119.40
Purchase #2	$86.96	3.384%	$89.9027	$89.90	$89.90	$89.90
Purchase #3	$159.71	3.780%	$165.747	$165.75	$165.75	$165.70
Purchase #4	$146.50	10.709%	$162.1887	$162.19	$162.20	$162.20
Purchase #5	$119.53	9.807%	$131.2523	$131.25	$131.25	$131.30
Purchase #6	$36.70	7.854%	$39.5824	$39.58	$39.60	$39.60
Purchase #7	$130.53	3.224%	$134.7383	$134.74	$134.75	$134.70
7 purchase totals =	$793.18		$842.8494	$842.85	$842.90	$842.80