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	$99.97	13.275%	$113.241	$113.24	$113.25	$113.20
Purchase #2	$148.28	3.793%	$153.9043	$153.90	$153.90	$153.90
Purchase #3	$127.94	12.862%	$144.3956	$144.40	$144.40	$144.40
Purchase #4	$135.66	12.623%	$152.7844	$152.78	$152.80	$152.80
Purchase #5	$43.95	4.628%	$45.984	$45.98	$46.00	$46.00
Purchase #6	$239.97	10.642%	$265.5076	$265.51	$265.50	$265.50
Purchase #7	$138.73	4.285%	$144.6746	$144.67	$144.65	$144.70
7 purchase totals =	$934.50		$1,020.4915	$1,020.48	$1,020.50	$1,020.50