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	$61.36	10.577%	$67.85	$67.85	$67.85	$67.90
Purchase #2	$83.95	5.191%	$88.3078	$88.31	$88.30	$88.30
Purchase #3	$136.34	12.853%	$153.8638	$153.86	$153.85	$153.90
Purchase #4	$44.57	6.274%	$47.3663	$47.37	$47.35	$47.40
Purchase #5	$186.82	6.785%	$199.4957	$199.50	$199.50	$199.50
Purchase #6	$110.83	8.670%	$120.439	$120.44	$120.45	$120.40
Purchase #7	$131.37	7.442%	$141.1466	$141.15	$141.15	$141.10
7 purchase totals =	$755.24		$818.4692	$818.48	$818.45	$818.50