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	$109.59	4.831%	$114.8843	$114.88	$114.90	$114.90
Purchase #2	$223.48	10.479%	$246.8985	$246.90	$246.90	$246.90
Purchase #3	$235.89	7.178%	$252.8222	$252.82	$252.80	$252.80
Purchase #4	$143.90	11.289%	$160.1449	$160.14	$160.15	$160.10
Purchase #5	$217.87	11.309%	$242.5089	$242.51	$242.50	$242.50
Purchase #6	$206.78	8.240%	$223.8187	$223.82	$223.80	$223.80
Purchase #7	$228.81	11.497%	$255.1163	$255.12	$255.10	$255.10
7 purchase totals =	$1,366.32		$1,496.1938	$1,496.19	$1,496.15	$1,496.10