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	$160.83	6.712%	$171.6249	$171.62	$171.60	$171.60
Purchase #2	$134.32	12.611%	$151.2591	$151.26	$151.25	$151.30
Purchase #3	$148.25	5.443%	$156.3192	$156.32	$156.30	$156.30
Purchase #4	$232.50	7.870%	$250.7978	$250.80	$250.80	$250.80
Purchase #5	$152.45	10.804%	$168.9207	$168.92	$168.90	$168.90
Purchase #6	$222.77	4.512%	$232.8214	$232.82	$232.80	$232.80
Purchase #7	$171.90	8.782%	$186.9963	$187.00	$187.00	$187.00
7 purchase totals =	$1,223.02		$1,318.7394	$1,318.74	$1,318.65	$1,318.70