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	$221.45	7.503%	$238.0654	$238.07	$238.05	$238.10
Purchase #2	$15.89	12.111%	$17.8144	$17.81	$17.80	$17.80
Purchase #3	$198.50	10.611%	$219.5628	$219.56	$219.55	$219.60
Purchase #4	$90.32	11.272%	$100.5009	$100.50	$100.50	$100.50
Purchase #5	$187.66	9.597%	$205.6697	$205.67	$205.65	$205.70
Purchase #6	$144.84	11.266%	$161.1577	$161.16	$161.15	$161.20
Purchase #7	$94.78	4.259%	$98.8167	$98.82	$98.80	$98.80
7 purchase totals =	$953.44		$1,041.5876	$1,041.59	$1,041.50	$1,041.70