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	$41.33	11.799%	$46.2065	$46.21	$46.20	$46.20
Purchase #2	$65.52	10.795%	$72.5929	$72.59	$72.60	$72.60
Purchase #3	$181.67	3.216%	$187.5125	$187.51	$187.50	$187.50
Purchase #4	$203.63	10.762%	$225.5447	$225.54	$225.55	$225.50
Purchase #5	$61.26	8.136%	$66.2441	$66.24	$66.25	$66.20
Purchase #6	$106.83	7.472%	$114.8123	$114.81	$114.80	$114.80
Purchase #7	$242.32	12.834%	$273.4193	$273.42	$273.40	$273.40
7 purchase totals =	$902.56		$986.3323	$986.32	$986.30	$986.20