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	$29.84	10.456%	$32.9601	$32.96	$32.95	$33.00
Purchase #2	$79.99	7.173%	$85.7277	$85.73	$85.75	$85.70
Purchase #3	$40.80	11.377%	$45.4418	$45.44	$45.45	$45.40
Purchase #4	$43.45	4.668%	$45.4782	$45.48	$45.50	$45.50
Purchase #5	$101.44	6.644%	$108.1797	$108.18	$108.20	$108.20
Purchase #6	$79.80	6.374%	$84.8865	$84.89	$84.90	$84.90
Purchase #7	$148.81	12.665%	$167.6568	$167.66	$167.65	$167.70
7 purchase totals =	$524.13		$570.3308	$570.34	$570.40	$570.40