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	$182.59	7.473%	$196.235	$196.24	$196.25	$196.20
Purchase #2	$119.45	6.587%	$127.3182	$127.32	$127.30	$127.30
Purchase #3	$74.30	9.872%	$81.6349	$81.63	$81.65	$81.60
Purchase #4	$35.29	11.228%	$39.2524	$39.25	$39.25	$39.30
Purchase #5	$25.85	8.632%	$28.0814	$28.08	$28.10	$28.10
Purchase #6	$169.93	3.725%	$176.2599	$176.26	$176.25	$176.30
Purchase #7	$58.93	6.667%	$62.8589	$62.86	$62.85	$62.90
7 purchase totals =	$666.34		$711.6407	$711.64	$711.65	$711.70