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	$162.54	9.299%	$177.6546	$177.65	$177.65	$177.70
Purchase #2	$63.42	9.624%	$69.5235	$69.52	$69.50	$69.50
Purchase #3	$75.89	10.433%	$83.8076	$83.81	$83.80	$83.80
Purchase #4	$83.49	3.315%	$86.2577	$86.26	$86.25	$86.30
Purchase #5	$83.93	6.233%	$89.1614	$89.16	$89.15	$89.20
Purchase #6	$225.29	5.656%	$238.0324	$238.03	$238.05	$238.00
Purchase #7	$35.67	12.528%	$40.1387	$40.14	$40.15	$40.10
7 purchase totals =	$730.23		$784.5759	$784.57	$784.55	$784.60