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	$153.50	5.619%	$162.1252	$162.13	$162.15	$162.10
Purchase #2	$237.29	11.496%	$264.5689	$264.57	$264.55	$264.60
Purchase #3	$57.47	13.730%	$65.3606	$65.36	$65.35	$65.40
Purchase #4	$33.47	11.599%	$37.3522	$37.35	$37.35	$37.40
Purchase #5	$242.81	12.530%	$273.2341	$273.23	$273.25	$273.20
Purchase #6	$92.76	10.244%	$102.2623	$102.26	$102.25	$102.30
Purchase #7	$148.79	4.503%	$155.49	$155.49	$155.50	$155.50
7 purchase totals =	$966.09		$1,060.3933	$1,060.39	$1,060.40	$1,060.50