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	$174.89	8.627%	$189.9778	$189.98	$190.00	$190.00
Purchase #2	$208.37	10.740%	$230.7489	$230.75	$230.75	$230.70
Purchase #3	$47.83	9.801%	$52.5178	$52.52	$52.50	$52.50
Purchase #4	$183.36	7.312%	$196.7673	$196.77	$196.75	$196.80
Purchase #5	$85.72	3.850%	$89.0202	$89.02	$89.00	$89.00
Purchase #6	$122.27	12.664%	$137.7543	$137.75	$137.75	$137.80
Purchase #7	$8.92	9.632%	$9.7792	$9.78	$9.80	$9.80
7 purchase totals =	$831.36		$906.5655	$906.57	$906.55	$906.60