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	$59.96	3.402%	$61.9998	$62.00	$62.00	$62.00
Purchase #2	$90.43	10.143%	$99.6023	$99.60	$99.60	$99.60
Purchase #3	$216.40	9.803%	$237.6137	$237.61	$237.60	$237.60
Purchase #4	$151.52	7.197%	$162.4249	$162.42	$162.40	$162.40
Purchase #5	$78.82	9.597%	$86.3844	$86.38	$86.40	$86.40
Purchase #6	$191.32	8.542%	$207.6626	$207.66	$207.65	$207.70
Purchase #7	$125.91	12.817%	$142.0479	$142.05	$142.05	$142.00
7 purchase totals =	$914.36		$997.7356	$997.72	$997.70	$997.70