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	$209.77	3.157%	$216.3924	$216.39	$216.40	$216.40
Purchase #2	$38.91	12.480%	$43.766	$43.77	$43.75	$43.80
Purchase #3	$213.86	4.173%	$222.7844	$222.78	$222.80	$222.80
Purchase #4	$137.46	10.853%	$152.3785	$152.38	$152.40	$152.40
Purchase #5	$189.34	10.294%	$208.8307	$208.83	$208.85	$208.80
Purchase #6	$45.52	3.147%	$46.9525	$46.95	$46.95	$47.00
Purchase #7	$92.69	11.599%	$103.4411	$103.44	$103.45	$103.40
7 purchase totals =	$927.55		$994.5456	$994.54	$994.60	$994.60