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	$104.68	5.293%	$110.2207	$110.22	$110.20	$110.20
Purchase #2	$240.55	9.391%	$263.1401	$263.14	$263.15	$263.10
Purchase #3	$39.75	6.225%	$42.2244	$42.22	$42.20	$42.20
Purchase #4	$46.78	9.610%	$51.2756	$51.28	$51.30	$51.30
Purchase #5	$57.86	3.508%	$59.8897	$59.89	$59.90	$59.90
Purchase #6	$175.93	9.542%	$192.7172	$192.72	$192.70	$192.70
Purchase #7	$33.72	3.677%	$34.9599	$34.96	$34.95	$35.00
7 purchase totals =	$699.27		$754.4276	$754.43	$754.40	$754.40