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	$110.57	5.700%	$116.8725	$116.87	$116.85	$116.90
Purchase #2	$78.87	13.402%	$89.4402	$89.44	$89.45	$89.40
Purchase #3	$208.97	7.686%	$225.0314	$225.03	$225.05	$225.00
Purchase #4	$88.40	10.393%	$97.5874	$97.59	$97.60	$97.60
Purchase #5	$132.78	11.237%	$147.7005	$147.70	$147.70	$147.70
Purchase #6	$179.32	10.120%	$197.4672	$197.47	$197.45	$197.50
Purchase #7	$69.60	3.236%	$71.8523	$71.85	$71.85	$71.90
7 purchase totals =	$868.51		$945.9515	$945.95	$945.95	$946.00