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	$168.47	13.586%	$191.3583	$191.36	$191.35	$191.40
Purchase #2	$200.72	13.523%	$227.8634	$227.86	$227.85	$227.90
Purchase #3	$37.28	9.600%	$40.8589	$40.86	$40.85	$40.90
Purchase #4	$203.70	4.631%	$213.1333	$213.13	$213.15	$213.10
Purchase #5	$61.89	3.650%	$64.149	$64.15	$64.15	$64.10
Purchase #6	$124.49	11.103%	$138.3121	$138.31	$138.30	$138.30
Purchase #7	$28.42	9.659%	$31.1651	$31.17	$31.15	$31.20
7 purchase totals =	$824.97		$906.8401	$906.84	$906.80	$906.90