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	$219.29	12.265%	$246.1859	$246.19	$246.20	$246.20
Purchase #2	$92.25	3.834%	$95.7869	$95.79	$95.80	$95.80
Purchase #3	$162.34	11.689%	$181.3159	$181.32	$181.30	$181.30
Purchase #4	$33.88	3.183%	$34.9584	$34.96	$34.95	$35.00
Purchase #5	$157.93	6.546%	$168.2681	$168.27	$168.25	$168.30
Purchase #6	$64.89	8.504%	$70.4082	$70.41	$70.40	$70.40
Purchase #7	$120.31	9.672%	$131.9464	$131.95	$131.95	$131.90
7 purchase totals =	$850.89		$928.8698	$928.89	$928.85	$928.90