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	$184.74	6.598%	$196.9291	$196.93	$196.95	$196.90
Purchase #2	$85.78	5.264%	$90.2955	$90.30	$90.30	$90.30
Purchase #3	$208.93	13.803%	$237.7686	$237.77	$237.75	$237.80
Purchase #4	$161.77	6.813%	$172.7914	$172.79	$172.80	$172.80
Purchase #5	$20.65	3.618%	$21.3971	$21.40	$21.40	$21.40
Purchase #6	$169.71	11.521%	$189.2623	$189.26	$189.25	$189.30
Purchase #7	$225.93	12.802%	$254.8536	$254.85	$254.85	$254.90
7 purchase totals =	$1,057.51		$1,163.2976	$1,163.30	$1,163.30	$1,163.40