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	$166.77	6.144%	$177.0163	$177.02	$177.00	$177.00
Purchase #2	$118.57	11.256%	$131.9162	$131.92	$131.90	$131.90
Purchase #3	$103.92	7.827%	$112.0538	$112.05	$112.05	$112.10
Purchase #4	$91.90	3.797%	$95.3894	$95.39	$95.40	$95.40
Purchase #5	$68.61	5.630%	$72.4727	$72.47	$72.45	$72.50
Purchase #6	$172.89	10.842%	$191.6347	$191.63	$191.65	$191.60
Purchase #7	$69.97	4.383%	$73.0368	$73.04	$73.05	$73.00
7 purchase totals =	$792.63		$853.5199	$853.52	$853.50	$853.50