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	$200.32	8.628%	$217.6036	$217.60	$217.60	$217.60
Purchase #2	$125.26	11.793%	$140.0319	$140.03	$140.05	$140.00
Purchase #3	$184.85	4.284%	$192.769	$192.77	$192.75	$192.80
Purchase #4	$204.90	8.870%	$223.0746	$223.07	$223.05	$223.10
Purchase #5	$134.41	8.247%	$145.4948	$145.49	$145.50	$145.50
Purchase #6	$112.86	9.741%	$123.8537	$123.85	$123.85	$123.90
Purchase #7	$131.90	12.655%	$148.5919	$148.59	$148.60	$148.60
7 purchase totals =	$1,094.50		$1,191.4195	$1,191.40	$1,191.40	$1,191.50