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	$57.32	7.156%	$61.4218	$61.42	$61.40	$61.40
Purchase #2	$181.49	10.652%	$200.8223	$200.82	$200.80	$200.80
Purchase #3	$26.25	13.248%	$29.7276	$29.73	$29.75	$29.70
Purchase #4	$150.49	11.277%	$167.4608	$167.46	$167.45	$167.50
Purchase #5	$215.39	3.345%	$222.5948	$222.59	$222.60	$222.60
Purchase #6	$167.47	7.676%	$180.325	$180.33	$180.35	$180.30
Purchase #7	$170.94	13.219%	$193.5366	$193.54	$193.55	$193.50
7 purchase totals =	$969.35		$1,055.8889	$1,055.89	$1,055.90	$1,055.80