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	$191.32	9.494%	$209.4839	$209.48	$209.50	$209.50
Purchase #2	$51.64	7.174%	$55.3447	$55.34	$55.35	$55.30
Purchase #3	$198.44	9.476%	$217.2442	$217.24	$217.25	$217.20
Purchase #4	$179.60	7.198%	$192.5276	$192.53	$192.55	$192.50
Purchase #5	$172.66	9.732%	$189.4633	$189.46	$189.45	$189.50
Purchase #6	$168.64	8.526%	$183.0182	$183.02	$183.00	$183.00
Purchase #7	$49.83	13.250%	$56.4325	$56.43	$56.45	$56.40
7 purchase totals =	$1,012.13		$1,103.5144	$1,103.50	$1,103.55	$1,103.40