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	$54.83	12.471%	$61.6678	$61.67	$61.65	$61.70
Purchase #2	$142.70	5.775%	$150.9409	$150.94	$150.95	$150.90
Purchase #3	$89.50	11.141%	$99.4712	$99.47	$99.45	$99.50
Purchase #4	$154.89	9.759%	$170.0057	$170.01	$170.00	$170.00
Purchase #5	$228.45	3.730%	$236.9712	$236.97	$236.95	$237.00
Purchase #6	$56.53	3.113%	$58.2898	$58.29	$58.30	$58.30
Purchase #7	$80.81	11.112%	$89.7896	$89.79	$89.80	$89.80
7 purchase totals =	$807.71		$867.1362	$867.14	$867.10	$867.20