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	$186.96	11.610%	$208.6661	$208.67	$208.65	$208.70
Purchase #2	$188.60	4.374%	$196.8494	$196.85	$196.85	$196.80
Purchase #3	$35.75	6.487%	$38.0691	$38.07	$38.05	$38.10
Purchase #4	$213.91	11.147%	$237.7545	$237.75	$237.75	$237.80
Purchase #5	$35.45	9.538%	$38.8312	$38.83	$38.85	$38.80
Purchase #6	$206.50	7.516%	$222.0205	$222.02	$222.00	$222.00
Purchase #7	$71.36	9.295%	$77.9929	$77.99	$78.00	$78.00
7 purchase totals =	$938.53		$1,020.1837	$1,020.18	$1,020.15	$1,020.20