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	$140.37	3.374%	$145.1061	$145.11	$145.10	$145.10
Purchase #2	$24.89	11.793%	$27.8253	$27.83	$27.85	$27.80
Purchase #3	$42.47	7.157%	$45.5096	$45.51	$45.50	$45.50
Purchase #4	$199.59	10.706%	$220.9581	$220.96	$220.95	$221.00
Purchase #5	$90.71	4.244%	$94.5597	$94.56	$94.55	$94.60
Purchase #6	$41.37	5.349%	$43.5829	$43.58	$43.60	$43.60
Purchase #7	$54.90	4.328%	$57.2761	$57.28	$57.30	$57.30
7 purchase totals =	$594.30		$634.8178	$634.83	$634.85	$634.90