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	$75.27	13.568%	$85.4826	$85.48	$85.50	$85.50
Purchase #2	$55.53	9.861%	$61.0058	$61.01	$61.00	$61.00
Purchase #3	$168.32	3.244%	$173.7803	$173.78	$173.80	$173.80
Purchase #4	$234.28	13.382%	$265.6313	$265.63	$265.65	$265.60
Purchase #5	$242.34	7.769%	$261.1674	$261.17	$261.15	$261.20
Purchase #6	$86.97	3.589%	$90.0914	$90.09	$90.10	$90.10
Purchase #7	$221.96	13.837%	$252.6726	$252.67	$252.65	$252.70
7 purchase totals =	$1,084.67		$1,189.8314	$1,189.83	$1,189.85	$1,189.90