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	$167.34	10.861%	$185.5148	$185.51	$185.50	$185.50
Purchase #2	$187.41	11.589%	$209.1289	$209.13	$209.15	$209.10
Purchase #3	$225.99	8.800%	$245.8771	$245.88	$245.90	$245.90
Purchase #4	$233.32	7.855%	$251.6473	$251.65	$251.65	$251.60
Purchase #5	$114.63	11.852%	$128.2159	$128.22	$128.20	$128.20
Purchase #6	$14.41	8.609%	$15.6506	$15.65	$15.65	$15.70
Purchase #7	$56.77	6.511%	$60.4663	$60.47	$60.45	$60.50
7 purchase totals =	$999.87		$1,096.5009	$1,096.51	$1,096.50	$1,096.50