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	$116.46	12.495%	$131.0117	$131.01	$131.00	$131.00
Purchase #2	$167.97	9.226%	$183.4669	$183.47	$183.45	$183.50
Purchase #3	$144.38	8.228%	$156.2596	$156.26	$156.25	$156.30
Purchase #4	$42.33	9.804%	$46.48	$46.48	$46.50	$46.50
Purchase #5	$170.51	6.536%	$181.6545	$181.65	$181.65	$181.70
Purchase #6	$82.64	11.838%	$92.4229	$92.42	$92.40	$92.40
Purchase #7	$228.45	6.700%	$243.7562	$243.76	$243.75	$243.80
7 purchase totals =	$952.74		$1,035.0518	$1,035.05	$1,035.00	$1,035.20