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	$106.76	11.267%	$118.7886	$118.79	$118.80	$118.80
Purchase #2	$209.74	9.409%	$229.4744	$229.47	$229.45	$229.50
Purchase #3	$242.78	5.570%	$256.3028	$256.30	$256.30	$256.30
Purchase #4	$78.49	13.646%	$89.2007	$89.20	$89.20	$89.20
Purchase #5	$14.73	3.620%	$15.2632	$15.26	$15.25	$15.30
Purchase #6	$60.84	7.691%	$65.5192	$65.52	$65.50	$65.50
Purchase #7	$169.43	6.796%	$180.9445	$180.94	$180.95	$180.90
7 purchase totals =	$882.77		$955.4934	$955.48	$955.45	$955.50