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	$138.56	13.578%	$157.3737	$157.37	$157.35	$157.40
Purchase #2	$214.95	11.824%	$240.3657	$240.37	$240.35	$240.40
Purchase #3	$35.27	5.365%	$37.1622	$37.16	$37.15	$37.20
Purchase #4	$216.70	10.513%	$239.4817	$239.48	$239.50	$239.50
Purchase #5	$83.77	6.602%	$89.3005	$89.30	$89.30	$89.30
Purchase #6	$225.27	7.267%	$241.6404	$241.64	$241.65	$241.60
Purchase #7	$39.38	5.862%	$41.6885	$41.69	$41.70	$41.70
7 purchase totals =	$953.90		$1,047.0127	$1,047.01	$1,047.00	$1,047.10