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	$234.31	7.653%	$252.2417	$252.24	$252.25	$252.20
Purchase #2	$157.87	6.123%	$167.5364	$167.54	$167.55	$167.50
Purchase #3	$246.61	3.764%	$255.8924	$255.89	$255.90	$255.90
Purchase #4	$76.96	6.272%	$81.7869	$81.79	$81.80	$81.80
Purchase #5	$234.49	5.709%	$247.877	$247.88	$247.90	$247.90
Purchase #6	$80.70	7.624%	$86.8526	$86.85	$86.85	$86.90
Purchase #7	$29.67	5.636%	$31.3422	$31.34	$31.35	$31.30
7 purchase totals =	$1,060.61		$1,123.5292	$1,123.53	$1,123.60	$1,123.50