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	$205.87	3.448%	$212.9684	$212.97	$212.95	$213.00
Purchase #2	$209.49	4.440%	$218.7914	$218.79	$218.80	$218.80
Purchase #3	$50.45	5.248%	$53.0976	$53.10	$53.10	$53.10
Purchase #4	$90.51	5.497%	$95.4853	$95.49	$95.50	$95.50
Purchase #5	$85.26	5.356%	$89.8265	$89.83	$89.85	$89.80
Purchase #6	$40.58	7.398%	$43.5821	$43.58	$43.60	$43.60
Purchase #7	$242.45	12.309%	$272.2932	$272.29	$272.30	$272.30
7 purchase totals =	$924.61		$986.0445	$986.05	$986.10	$986.10