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	$60.42	4.417%	$63.0888	$63.09	$63.10	$63.10
Purchase #2	$178.46	4.118%	$185.809	$185.81	$185.80	$185.80
Purchase #3	$220.90	9.747%	$242.4311	$242.43	$242.45	$242.40
Purchase #4	$174.88	5.460%	$184.4284	$184.43	$184.45	$184.40
Purchase #5	$236.73	10.397%	$261.3428	$261.34	$261.35	$261.30
Purchase #6	$202.48	9.867%	$222.4587	$222.46	$222.45	$222.50
Purchase #7	$100.46	4.696%	$105.1776	$105.18	$105.20	$105.20
7 purchase totals =	$1,174.33		$1,264.7364	$1,264.74	$1,264.80	$1,264.70