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	$81.67	11.105%	$90.7395	$90.74	$90.75	$90.70
Purchase #2	$205.92	6.594%	$219.4984	$219.50	$219.50	$219.50
Purchase #3	$63.61	13.613%	$72.2692	$72.27	$72.25	$72.30
Purchase #4	$50.52	8.258%	$54.6919	$54.69	$54.70	$54.70
Purchase #5	$111.48	11.270%	$124.0438	$124.04	$124.05	$124.00
Purchase #6	$105.99	8.381%	$114.873	$114.87	$114.85	$114.90
Purchase #7	$124.59	13.129%	$140.9474	$140.95	$140.95	$140.90
7 purchase totals =	$743.78		$817.0632	$817.06	$817.05	$817.00