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	$31.45	11.495%	$35.0652	$35.07	$35.05	$35.10
Purchase #2	$102.99	8.570%	$111.8162	$111.82	$111.80	$111.80
Purchase #3	$250.50	12.696%	$282.3035	$282.30	$282.30	$282.30
Purchase #4	$227.73	13.339%	$258.1069	$258.11	$258.10	$258.10
Purchase #5	$128.26	7.213%	$137.5114	$137.51	$137.50	$137.50
Purchase #6	$51.65	11.665%	$57.675	$57.68	$57.70	$57.70
Purchase #7	$244.25	10.583%	$270.099	$270.10	$270.10	$270.10
7 purchase totals =	$1,036.83		$1,152.5772	$1,152.59	$1,152.55	$1,152.60