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	$61.96	7.850%	$66.8239	$66.82	$66.80	$66.80
Purchase #2	$19.72	8.276%	$21.352	$21.35	$21.35	$21.40
Purchase #3	$164.31	13.756%	$186.9125	$186.91	$186.90	$186.90
Purchase #4	$200.69	4.111%	$208.9404	$208.94	$208.95	$208.90
Purchase #5	$79.28	7.282%	$85.0532	$85.05	$85.05	$85.10
Purchase #6	$129.56	6.460%	$137.9296	$137.93	$137.95	$137.90
Purchase #7	$105.38	11.786%	$117.8001	$117.80	$117.80	$117.80
7 purchase totals =	$760.90		$824.8117	$824.80	$824.80	$824.80