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	$178.79	11.824%	$199.9301	$199.93	$199.95	$199.90
Purchase #2	$40.78	4.298%	$42.5327	$42.53	$42.55	$42.50
Purchase #3	$101.52	7.867%	$109.5066	$109.51	$109.50	$109.50
Purchase #4	$241.77	5.648%	$255.4252	$255.43	$255.45	$255.40
Purchase #5	$147.71	11.620%	$164.8739	$164.87	$164.85	$164.90
Purchase #6	$16.80	6.196%	$17.8409	$17.84	$17.85	$17.80
Purchase #7	$93.27	3.523%	$96.5559	$96.56	$96.55	$96.60
7 purchase totals =	$820.64		$886.6653	$886.67	$886.70	$886.60