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	$83.74	7.151%	$89.7282	$89.73	$89.75	$89.70
Purchase #2	$185.35	6.207%	$196.8547	$196.85	$196.85	$196.90
Purchase #3	$133.27	7.556%	$143.3399	$143.34	$143.35	$143.30
Purchase #4	$95.26	11.836%	$106.535	$106.54	$106.55	$106.50
Purchase #5	$116.89	13.127%	$132.2342	$132.23	$132.25	$132.20
Purchase #6	$204.44	4.408%	$213.4517	$213.45	$213.45	$213.50
Purchase #7	$28.29	4.708%	$29.6219	$29.62	$29.60	$29.60
7 purchase totals =	$847.24		$911.7656	$911.76	$911.80	$911.70