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	$126.81	11.427%	$141.3006	$141.30	$141.30	$141.30
Purchase #2	$80.28	7.274%	$86.1196	$86.12	$86.10	$86.10
Purchase #3	$86.25	4.829%	$90.415	$90.42	$90.40	$90.40
Purchase #4	$210.35	11.105%	$233.7094	$233.71	$233.70	$233.70
Purchase #5	$59.91	4.682%	$62.715	$62.72	$62.70	$62.70
Purchase #6	$97.61	5.591%	$103.0674	$103.07	$103.05	$103.10
Purchase #7	$197.58	10.829%	$218.9759	$218.98	$219.00	$219.00
7 purchase totals =	$858.79		$936.3029	$936.32	$936.25	$936.30