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	$27.63	5.127%	$29.0466	$29.05	$29.05	$29.00
Purchase #2	$19.41	12.768%	$21.8883	$21.89	$21.90	$21.90
Purchase #3	$196.67	9.566%	$215.4835	$215.48	$215.50	$215.50
Purchase #4	$55.45	4.670%	$58.0395	$58.04	$58.05	$58.00
Purchase #5	$187.93	4.616%	$196.6048	$196.60	$196.60	$196.60
Purchase #6	$162.56	6.292%	$172.7883	$172.79	$172.80	$172.80
Purchase #7	$146.62	6.258%	$155.7955	$155.80	$155.80	$155.80
7 purchase totals =	$796.27		$849.6465	$849.65	$849.70	$849.60