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	$22.83	5.229%	$24.0238	$24.02	$24.00	$24.00
Purchase #2	$112.27	10.215%	$123.7384	$123.74	$123.75	$123.70
Purchase #3	$151.78	9.413%	$166.0671	$166.07	$166.05	$166.10
Purchase #4	$170.98	13.799%	$194.5735	$194.57	$194.55	$194.60
Purchase #5	$39.56	8.275%	$42.8336	$42.83	$42.85	$42.80
Purchase #6	$211.97	13.727%	$241.0671	$241.07	$241.05	$241.10
Purchase #7	$165.81	6.149%	$176.0057	$176.01	$176.00	$176.00
7 purchase totals =	$875.20		$968.3092	$968.31	$968.25	$968.30