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	$95.97	7.869%	$103.5219	$103.52	$103.50	$103.50
Purchase #2	$144.90	10.256%	$159.7609	$159.76	$159.75	$159.80
Purchase #3	$195.70	10.290%	$215.8375	$215.84	$215.85	$215.80
Purchase #4	$166.62	3.554%	$172.5417	$172.54	$172.55	$172.50
Purchase #5	$100.56	3.158%	$103.7357	$103.74	$103.75	$103.70
Purchase #6	$95.93	9.566%	$105.1067	$105.11	$105.10	$105.10
Purchase #7	$31.37	12.684%	$35.349	$35.35	$35.35	$35.30
7 purchase totals =	$831.05		$895.8534	$895.86	$895.85	$895.70