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	$76.62	12.487%	$86.1875	$86.19	$86.20	$86.20
Purchase #2	$220.29	8.467%	$238.942	$238.94	$238.95	$238.90
Purchase #3	$20.81	4.134%	$21.6703	$21.67	$21.65	$21.70
Purchase #4	$73.38	12.527%	$82.5723	$82.57	$82.55	$82.60
Purchase #5	$153.88	6.766%	$164.2915	$164.29	$164.30	$164.30
Purchase #6	$43.66	3.315%	$45.1073	$45.11	$45.10	$45.10
Purchase #7	$202.28	6.172%	$214.7647	$214.76	$214.75	$214.80
7 purchase totals =	$790.92		$853.5356	$853.53	$853.50	$853.60