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	$233.85	3.547%	$242.1447	$242.14	$242.15	$242.10
Purchase #2	$156.28	3.761%	$162.1577	$162.16	$162.15	$162.20
Purchase #3	$243.98	7.129%	$261.3733	$261.37	$261.35	$261.40
Purchase #4	$102.37	10.429%	$113.0462	$113.05	$113.05	$113.00
Purchase #5	$93.63	6.611%	$99.8199	$99.82	$99.80	$99.80
Purchase #6	$62.87	5.432%	$66.2851	$66.29	$66.30	$66.30
Purchase #7	$73.93	13.240%	$83.7183	$83.72	$83.70	$83.70
7 purchase totals =	$966.91		$1,028.5452	$1,028.55	$1,028.50	$1,028.50