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	$186.47	12.116%	$209.0627	$209.06	$209.05	$209.10
Purchase #2	$145.97	6.679%	$155.7193	$155.72	$155.70	$155.70
Purchase #3	$84.34	7.176%	$90.3922	$90.39	$90.40	$90.40
Purchase #4	$139.98	7.780%	$150.8704	$150.87	$150.85	$150.90
Purchase #5	$79.82	3.393%	$82.5283	$82.53	$82.55	$82.50
Purchase #6	$235.49	11.155%	$261.7589	$261.76	$261.75	$261.80
Purchase #7	$16.34	6.418%	$17.3887	$17.39	$17.40	$17.40
7 purchase totals =	$888.41		$967.7205	$967.72	$967.70	$967.80