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	$172.32	4.115%	$179.411	$179.41	$179.40	$179.40
Purchase #2	$37.33	3.808%	$38.7515	$38.75	$38.75	$38.80
Purchase #3	$117.96	4.484%	$123.2493	$123.25	$123.25	$123.20
Purchase #4	$53.54	11.226%	$59.5504	$59.55	$59.55	$59.60
Purchase #5	$250.88	10.868%	$278.1456	$278.15	$278.15	$278.10
Purchase #6	$175.61	13.237%	$198.8555	$198.86	$198.85	$198.90
Purchase #7	$192.82	3.219%	$199.0269	$199.03	$199.05	$199.00
7 purchase totals =	$1,000.46		$1,076.9902	$1,077.00	$1,077.00	$1,077.00