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	$223.94	3.441%	$231.6458	$231.65	$231.65	$231.60
Purchase #2	$242.60	7.870%	$261.6926	$261.69	$261.70	$261.70
Purchase #3	$10.30	4.437%	$10.757	$10.76	$10.75	$10.80
Purchase #4	$146.29	12.732%	$164.9156	$164.92	$164.90	$164.90
Purchase #5	$228.48	4.658%	$239.1226	$239.12	$239.10	$239.10
Purchase #6	$67.53	7.336%	$72.484	$72.48	$72.50	$72.50
Purchase #7	$249.98	10.222%	$275.533	$275.53	$275.55	$275.50
7 purchase totals =	$1,169.12		$1,256.1506	$1,256.15	$1,256.15	$1,256.10