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	$40.38	6.171%	$42.8718	$42.87	$42.85	$42.90
Purchase #2	$119.73	3.175%	$123.5314	$123.53	$123.55	$123.50
Purchase #3	$196.78	11.268%	$218.9532	$218.95	$218.95	$219.00
Purchase #4	$172.49	7.732%	$185.8269	$185.83	$185.85	$185.80
Purchase #5	$127.44	13.445%	$144.5743	$144.57	$144.55	$144.60
Purchase #6	$211.63	12.679%	$238.4626	$238.46	$238.45	$238.50
Purchase #7	$146.42	4.388%	$152.8449	$152.84	$152.85	$152.80
7 purchase totals =	$1,014.87		$1,107.0651	$1,107.05	$1,107.05	$1,107.10