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	$45.69	7.277%	$49.0149	$49.01	$49.00	$49.00
Purchase #2	$189.59	13.254%	$214.7183	$214.72	$214.70	$214.70
Purchase #3	$213.32	4.764%	$223.4826	$223.48	$223.50	$223.50
Purchase #4	$143.73	11.385%	$160.0937	$160.09	$160.10	$160.10
Purchase #5	$140.76	5.524%	$148.5356	$148.54	$148.55	$148.50
Purchase #6	$140.68	10.633%	$155.6385	$155.64	$155.65	$155.60
Purchase #7	$178.46	6.627%	$190.2865	$190.29	$190.30	$190.30
7 purchase totals =	$1,052.23		$1,141.7701	$1,141.77	$1,141.80	$1,141.70