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	$12.97	8.610%	$14.0867	$14.09	$14.10	$14.10
Purchase #2	$42.42	6.219%	$45.0581	$45.06	$45.05	$45.10
Purchase #3	$229.50	4.112%	$238.937	$238.94	$238.95	$238.90
Purchase #4	$79.90	13.827%	$90.9478	$90.95	$90.95	$90.90
Purchase #5	$119.84	11.411%	$133.5149	$133.51	$133.50	$133.50
Purchase #6	$211.43	5.693%	$223.4667	$223.47	$223.45	$223.50
Purchase #7	$133.75	12.759%	$150.8152	$150.82	$150.80	$150.80
7 purchase totals =	$829.81		$896.8264	$896.84	$896.80	$896.80