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	$184.49	4.146%	$192.139	$192.14	$192.15	$192.10
Purchase #2	$189.73	12.549%	$213.5392	$213.54	$213.55	$213.50
Purchase #3	$83.88	7.595%	$90.2507	$90.25	$90.25	$90.30
Purchase #4	$148.26	13.479%	$168.244	$168.24	$168.25	$168.20
Purchase #5	$77.75	12.374%	$87.3708	$87.37	$87.35	$87.40
Purchase #6	$217.38	6.402%	$231.2967	$231.30	$231.30	$231.30
Purchase #7	$172.45	7.655%	$185.651	$185.65	$185.65	$185.70
7 purchase totals =	$1,073.94		$1,168.4914	$1,168.49	$1,168.50	$1,168.50