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	$32.70	6.841%	$34.937	$34.94	$34.95	$34.90
Purchase #2	$243.88	11.650%	$272.292	$272.29	$272.30	$272.30
Purchase #3	$148.79	13.119%	$168.3098	$168.31	$168.30	$168.30
Purchase #4	$176.86	3.242%	$182.5938	$182.59	$182.60	$182.60
Purchase #5	$83.87	13.143%	$94.893	$94.89	$94.90	$94.90
Purchase #6	$88.44	10.225%	$97.483	$97.48	$97.50	$97.50
Purchase #7	$192.33	6.459%	$204.7526	$204.75	$204.75	$204.80
7 purchase totals =	$966.87		$1,055.2612	$1,055.25	$1,055.30	$1,055.30