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	$83.31	3.777%	$86.4566	$86.46	$86.45	$86.50
Purchase #2	$174.80	6.340%	$185.8823	$185.88	$185.90	$185.90
Purchase #3	$91.83	4.436%	$95.9036	$95.90	$95.90	$95.90
Purchase #4	$176.74	6.399%	$188.0496	$188.05	$188.05	$188.00
Purchase #5	$161.76	6.802%	$172.7629	$172.76	$172.75	$172.80
Purchase #6	$122.82	6.874%	$131.2626	$131.26	$131.25	$131.30
Purchase #7	$6.44	9.183%	$7.0314	$7.03	$7.05	$7.00
7 purchase totals =	$817.70		$867.3490	$867.34	$867.35	$867.40