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	$95.57	9.361%	$104.5163	$104.52	$104.50	$104.50
Purchase #2	$79.75	12.562%	$89.7682	$89.77	$89.75	$89.80
Purchase #3	$53.34	10.660%	$59.026	$59.03	$59.05	$59.00
Purchase #4	$232.99	6.483%	$248.0947	$248.09	$248.10	$248.10
Purchase #5	$30.27	3.176%	$31.2314	$31.23	$31.25	$31.20
Purchase #6	$180.90	13.775%	$205.819	$205.82	$205.80	$205.80
Purchase #7	$22.88	7.621%	$24.6237	$24.62	$24.60	$24.60
7 purchase totals =	$695.70		$763.0793	$763.08	$763.05	$763.00