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	$225.98	6.693%	$241.1048	$241.10	$241.10	$241.10
Purchase #2	$67.70	6.771%	$72.284	$72.28	$72.30	$72.30
Purchase #3	$20.55	6.224%	$21.829	$21.83	$21.85	$21.80
Purchase #4	$44.47	3.228%	$45.9055	$45.91	$45.90	$45.90
Purchase #5	$42.86	3.838%	$44.505	$44.51	$44.50	$44.50
Purchase #6	$134.74	3.242%	$139.1083	$139.11	$139.10	$139.10
Purchase #7	$137.89	3.726%	$143.0278	$143.03	$143.05	$143.00
7 purchase totals =	$674.19		$707.7644	$707.77	$707.80	$707.70