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	$246.94	10.580%	$273.0663	$273.07	$273.05	$273.10
Purchase #2	$231.37	10.518%	$255.7055	$255.71	$255.70	$255.70
Purchase #3	$79.37	12.144%	$89.0087	$89.01	$89.00	$89.00
Purchase #4	$181.37	12.463%	$203.9741	$203.97	$203.95	$204.00
Purchase #5	$65.36	9.313%	$71.447	$71.45	$71.45	$71.40
Purchase #6	$212.42	7.752%	$228.8868	$228.89	$228.90	$228.90
Purchase #7	$35.37	5.754%	$37.4052	$37.41	$37.40	$37.40
7 purchase totals =	$1,052.20		$1,159.4936	$1,159.51	$1,159.45	$1,159.50