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	$24.50	5.389%	$25.8203	$25.82	$25.80	$25.80
Purchase #2	$70.57	11.686%	$78.8168	$78.82	$78.80	$78.80
Purchase #3	$212.73	3.576%	$220.3372	$220.34	$220.35	$220.30
Purchase #4	$86.42	5.235%	$90.9441	$90.94	$90.95	$90.90
Purchase #5	$82.74	10.367%	$91.3177	$91.32	$91.30	$91.30
Purchase #6	$61.93	8.662%	$67.2944	$67.29	$67.30	$67.30
Purchase #7	$182.98	3.276%	$188.9744	$188.97	$188.95	$189.00
7 purchase totals =	$721.87		$763.5049	$763.50	$763.45	$763.40