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	$97.79	6.681%	$104.3233	$104.32	$104.30	$104.30
Purchase #2	$157.27	10.478%	$173.7488	$173.75	$173.75	$173.70
Purchase #3	$102.29	9.794%	$112.3083	$112.31	$112.30	$112.30
Purchase #4	$36.68	11.495%	$40.8964	$40.90	$40.90	$40.90
Purchase #5	$225.40	13.541%	$255.9214	$255.92	$255.90	$255.90
Purchase #6	$112.84	6.793%	$120.5052	$120.51	$120.50	$120.50
Purchase #7	$212.51	13.705%	$241.6345	$241.63	$241.65	$241.60
7 purchase totals =	$944.78		$1,049.3379	$1,049.34	$1,049.30	$1,049.20