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	$52.42	4.126%	$54.5828	$54.58	$54.60	$54.60
Purchase #2	$93.88	7.517%	$100.937	$100.94	$100.95	$100.90
Purchase #3	$63.87	11.721%	$71.3562	$71.36	$71.35	$71.40
Purchase #4	$180.63	4.203%	$188.2219	$188.22	$188.20	$188.20
Purchase #5	$204.34	5.863%	$216.3205	$216.32	$216.30	$216.30
Purchase #6	$42.69	8.769%	$46.4335	$46.43	$46.45	$46.40
Purchase #7	$90.79	7.835%	$97.9034	$97.90	$97.90	$97.90
7 purchase totals =	$728.62		$775.7553	$775.75	$775.75	$775.70