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	$93.78	10.279%	$103.4196	$103.42	$103.40	$103.40
Purchase #2	$9.47	12.556%	$10.6591	$10.66	$10.65	$10.70
Purchase #3	$85.27	10.366%	$94.1091	$94.11	$94.10	$94.10
Purchase #4	$182.86	7.172%	$195.9747	$195.97	$195.95	$196.00
Purchase #5	$96.30	13.783%	$109.573	$109.57	$109.55	$109.60
Purchase #6	$169.80	9.108%	$185.2654	$185.27	$185.25	$185.30
Purchase #7	$63.83	8.773%	$69.4298	$69.43	$69.45	$69.40
7 purchase totals =	$701.31		$768.4307	$768.43	$768.35	$768.50