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	$69.63	12.527%	$78.3526	$78.35	$78.35	$78.40
Purchase #2	$236.51	3.149%	$243.9577	$243.96	$243.95	$244.00
Purchase #3	$24.57	13.702%	$27.9366	$27.94	$27.95	$27.90
Purchase #4	$23.90	12.560%	$26.9018	$26.90	$26.90	$26.90
Purchase #5	$228.67	11.436%	$254.8207	$254.82	$254.80	$254.80
Purchase #6	$66.62	9.396%	$72.8796	$72.88	$72.90	$72.90
Purchase #7	$31.96	12.197%	$35.8582	$35.86	$35.85	$35.90
7 purchase totals =	$681.86		$740.7072	$740.71	$740.70	$740.80