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	$100.29	3.708%	$104.0088	$104.01	$104.00	$104.00
Purchase #2	$42.84	5.689%	$45.2772	$45.28	$45.30	$45.30
Purchase #3	$95.45	6.670%	$101.8165	$101.82	$101.80	$101.80
Purchase #4	$26.98	3.795%	$28.0039	$28.00	$28.00	$28.00
Purchase #5	$11.73	4.850%	$12.2989	$12.30	$12.30	$12.30
Purchase #6	$139.37	12.580%	$156.9027	$156.90	$156.90	$156.90
Purchase #7	$25.25	11.261%	$28.0934	$28.09	$28.10	$28.10
7 purchase totals =	$441.91		$476.4014	$476.40	$476.40	$476.40