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	$180.59	5.290%	$190.1432	$190.14	$190.15	$190.10
Purchase #2	$168.80	13.438%	$191.4833	$191.48	$191.50	$191.50
Purchase #3	$224.30	8.351%	$243.0313	$243.03	$243.05	$243.00
Purchase #4	$250.42	4.597%	$261.9318	$261.93	$261.95	$261.90
Purchase #5	$34.56	6.311%	$36.7411	$36.74	$36.75	$36.70
Purchase #6	$180.51	13.727%	$205.2886	$205.29	$205.30	$205.30
Purchase #7	$123.25	6.427%	$131.1713	$131.17	$131.15	$131.20
7 purchase totals =	$1,162.43		$1,259.7906	$1,259.78	$1,259.85	$1,259.70