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	$34.83	6.651%	$37.1465	$37.15	$37.15	$37.10
Purchase #2	$42.33	3.503%	$43.8128	$43.81	$43.80	$43.80
Purchase #3	$11.37	9.764%	$12.4802	$12.48	$12.50	$12.50
Purchase #4	$138.34	11.504%	$154.2546	$154.25	$154.25	$154.30
Purchase #5	$124.50	11.405%	$138.6992	$138.70	$138.70	$138.70
Purchase #6	$36.33	9.641%	$39.8326	$39.83	$39.85	$39.80
Purchase #7	$56.53	9.811%	$62.0762	$62.08	$62.10	$62.10
7 purchase totals =	$444.23		$488.3021	$488.30	$488.35	$488.30