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	$137.84	11.630%	$153.8708	$153.87	$153.85	$153.90
Purchase #2	$94.82	6.303%	$100.7965	$100.80	$100.80	$100.80
Purchase #3	$195.97	6.825%	$209.345	$209.35	$209.35	$209.30
Purchase #4	$112.77	12.758%	$127.1572	$127.16	$127.15	$127.20
Purchase #5	$209.47	11.700%	$233.978	$233.98	$234.00	$234.00
Purchase #6	$127.47	5.669%	$134.6963	$134.70	$134.70	$134.70
Purchase #7	$200.34	13.734%	$227.8547	$227.85	$227.85	$227.90
7 purchase totals =	$1,078.68		$1,187.6985	$1,187.71	$1,187.70	$1,187.80