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	$219.30	5.590%	$231.5589	$231.56	$231.55	$231.60
Purchase #2	$100.75	4.441%	$105.2243	$105.22	$105.20	$105.20
Purchase #3	$38.91	9.824%	$42.7325	$42.73	$42.75	$42.70
Purchase #4	$138.40	12.239%	$155.3388	$155.34	$155.35	$155.30
Purchase #5	$199.58	9.493%	$218.5261	$218.53	$218.55	$218.50
Purchase #6	$157.93	9.147%	$172.3759	$172.38	$172.40	$172.40
Purchase #7	$86.46	9.719%	$94.863	$94.86	$94.85	$94.90
7 purchase totals =	$941.33		$1,020.6195	$1,020.62	$1,020.65	$1,020.60