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	$239.46	8.808%	$260.5516	$260.55	$260.55	$260.60
Purchase #2	$91.37	13.689%	$103.8776	$103.88	$103.90	$103.90
Purchase #3	$156.36	9.517%	$171.2408	$171.24	$171.25	$171.20
Purchase #4	$134.45	4.441%	$140.4209	$140.42	$140.40	$140.40
Purchase #5	$196.92	10.766%	$218.1204	$218.12	$218.10	$218.10
Purchase #6	$39.34	11.589%	$43.8991	$43.90	$43.90	$43.90
Purchase #7	$77.89	10.209%	$85.8418	$85.84	$85.85	$85.80
7 purchase totals =	$935.79		$1,023.9522	$1,023.95	$1,023.95	$1,023.90