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	$113.48	10.504%	$125.3999	$125.40	$125.40	$125.40
Purchase #2	$47.65	6.142%	$50.5767	$50.58	$50.60	$50.60
Purchase #3	$170.48	12.312%	$191.4695	$191.47	$191.45	$191.50
Purchase #4	$124.85	12.716%	$140.7259	$140.73	$140.75	$140.70
Purchase #5	$101.73	3.121%	$104.905	$104.91	$104.90	$104.90
Purchase #6	$242.80	8.429%	$263.2656	$263.27	$263.25	$263.30
Purchase #7	$113.54	8.583%	$123.2851	$123.29	$123.30	$123.30
7 purchase totals =	$914.53		$999.6277	$999.65	$999.65	$999.70