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	$56.96	11.179%	$63.3276	$63.33	$63.35	$63.30
Purchase #2	$201.98	6.872%	$215.8601	$215.86	$215.85	$215.90
Purchase #3	$79.73	5.229%	$83.8991	$83.90	$83.90	$83.90
Purchase #4	$238.42	11.224%	$265.1803	$265.18	$265.20	$265.20
Purchase #5	$164.40	6.816%	$175.6055	$175.61	$175.60	$175.60
Purchase #6	$60.77	7.699%	$65.4487	$65.45	$65.45	$65.40
Purchase #7	$188.73	6.310%	$200.6389	$200.64	$200.65	$200.60
7 purchase totals =	$990.99		$1,069.9602	$1,069.97	$1,070.00	$1,069.90