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	$31.52	4.775%	$33.0251	$33.03	$33.05	$33.00
Purchase #2	$16.40	9.870%	$18.0187	$18.02	$18.00	$18.00
Purchase #3	$98.46	10.730%	$109.0248	$109.02	$109.00	$109.00
Purchase #4	$69.56	10.523%	$76.8798	$76.88	$76.90	$76.90
Purchase #5	$166.40	8.401%	$180.3793	$180.38	$180.40	$180.40
Purchase #6	$12.73	9.191%	$13.9	$13.90	$13.90	$13.90
Purchase #7	$41.89	8.726%	$45.5453	$45.55	$45.55	$45.50
7 purchase totals =	$436.96		$476.7730	$476.78	$476.80	$476.70