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	$158.53	9.840%	$174.1294	$174.13	$174.15	$174.10
Purchase #2	$58.45	13.665%	$66.4372	$66.44	$66.45	$66.40
Purchase #3	$112.69	4.573%	$117.8433	$117.84	$117.85	$117.80
Purchase #4	$43.39	5.415%	$45.7396	$45.74	$45.75	$45.70
Purchase #5	$104.33	7.243%	$111.8866	$111.89	$111.90	$111.90
Purchase #6	$131.50	11.227%	$146.2635	$146.26	$146.25	$146.30
Purchase #7	$176.81	12.558%	$199.0138	$199.01	$199.00	$199.00
7 purchase totals =	$785.70		$861.3134	$861.31	$861.35	$861.20