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	$83.34	7.499%	$89.5897	$89.59	$89.60	$89.60
Purchase #2	$10.58	9.745%	$11.611	$11.61	$11.60	$11.60
Purchase #3	$60.63	10.519%	$67.0077	$67.01	$67.00	$67.00
Purchase #4	$201.44	5.211%	$211.937	$211.94	$211.95	$211.90
Purchase #5	$49.76	9.753%	$54.6131	$54.61	$54.60	$54.60
Purchase #6	$220.50	7.417%	$236.8545	$236.85	$236.85	$236.90
Purchase #7	$212.78	10.233%	$234.5538	$234.55	$234.55	$234.60
7 purchase totals =	$839.03		$906.1668	$906.16	$906.15	$906.20