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	$241.84	5.301%	$254.6599	$254.66	$254.65	$254.70
Purchase #2	$24.25	13.686%	$27.5689	$27.57	$27.55	$27.60
Purchase #3	$37.85	6.812%	$40.4283	$40.43	$40.45	$40.40
Purchase #4	$224.38	13.387%	$254.4178	$254.42	$254.40	$254.40
Purchase #5	$211.43	7.576%	$227.4479	$227.45	$227.45	$227.40
Purchase #6	$242.76	4.328%	$253.2667	$253.27	$253.25	$253.30
Purchase #7	$190.62	3.732%	$197.7339	$197.73	$197.75	$197.70
7 purchase totals =	$1,173.13		$1,255.5234	$1,255.53	$1,255.50	$1,255.50