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	$93.63	4.113%	$97.481	$97.48	$97.50	$97.50
Purchase #2	$196.34	3.800%	$203.8009	$203.80	$203.80	$203.80
Purchase #3	$17.35	8.689%	$18.8575	$18.86	$18.85	$18.90
Purchase #4	$70.47	9.742%	$77.3352	$77.34	$77.35	$77.30
Purchase #5	$86.89	4.197%	$90.5368	$90.54	$90.55	$90.50
Purchase #6	$143.64	8.152%	$155.3495	$155.35	$155.35	$155.30
Purchase #7	$79.91	8.443%	$86.6568	$86.66	$86.65	$86.70
7 purchase totals =	$688.23		$730.0177	$730.03	$730.05	$730.00