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	$151.39	13.649%	$172.0532	$172.05	$172.05	$172.10
Purchase #2	$55.99	5.297%	$58.9558	$58.96	$58.95	$59.00
Purchase #3	$247.39	8.458%	$268.3142	$268.31	$268.30	$268.30
Purchase #4	$141.60	5.545%	$149.4517	$149.45	$149.45	$149.50
Purchase #5	$143.89	3.392%	$148.7707	$148.77	$148.75	$148.80
Purchase #6	$192.96	12.747%	$217.5566	$217.56	$217.55	$217.60
Purchase #7	$82.64	3.210%	$85.2927	$85.29	$85.30	$85.30
7 purchase totals =	$1,015.86		$1,100.3949	$1,100.39	$1,100.35	$1,100.60