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	$204.58	5.729%	$216.3004	$216.30	$216.30	$216.30
Purchase #2	$11.80	12.598%	$13.2866	$13.29	$13.30	$13.30
Purchase #3	$224.30	4.111%	$233.521	$233.52	$233.50	$233.50
Purchase #4	$73.78	6.809%	$78.8037	$78.80	$78.80	$78.80
Purchase #5	$63.79	11.523%	$71.1405	$71.14	$71.15	$71.10
Purchase #6	$241.42	9.869%	$265.2457	$265.25	$265.25	$265.20
Purchase #7	$192.51	7.778%	$207.4834	$207.48	$207.50	$207.50
7 purchase totals =	$1,012.18		$1,085.7813	$1,085.78	$1,085.80	$1,085.70