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	$196.56	3.112%	$202.6769	$202.68	$202.70	$202.70
Purchase #2	$43.39	11.387%	$48.3308	$48.33	$48.35	$48.30
Purchase #3	$130.48	8.709%	$141.8435	$141.84	$141.85	$141.80
Purchase #4	$52.43	13.259%	$59.3817	$59.38	$59.40	$59.40
Purchase #5	$89.68	6.584%	$95.5845	$95.58	$95.60	$95.60
Purchase #6	$243.68	12.400%	$273.8963	$273.90	$273.90	$273.90
Purchase #7	$81.68	13.216%	$92.4748	$92.47	$92.45	$92.50
7 purchase totals =	$837.90		$914.1885	$914.18	$914.25	$914.20