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	$97.85	11.698%	$109.2965	$109.30	$109.30	$109.30
Purchase #2	$140.58	5.172%	$147.8508	$147.85	$147.85	$147.90
Purchase #3	$162.50	7.217%	$174.2276	$174.23	$174.25	$174.20
Purchase #4	$37.46	13.174%	$42.395	$42.40	$42.40	$42.40
Purchase #5	$81.46	7.282%	$87.3919	$87.39	$87.40	$87.40
Purchase #6	$237.70	9.865%	$261.1491	$261.15	$261.15	$261.10
Purchase #7	$37.46	9.801%	$41.1315	$41.13	$41.15	$41.10
7 purchase totals =	$795.01		$863.4424	$863.45	$863.50	$863.40