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	$111.31	13.850%	$126.7264	$126.73	$126.75	$126.70
Purchase #2	$206.98	7.258%	$222.0026	$222.00	$222.00	$222.00
Purchase #3	$78.80	13.426%	$89.3797	$89.38	$89.40	$89.40
Purchase #4	$63.34	10.346%	$69.8932	$69.89	$69.90	$69.90
Purchase #5	$38.72	13.358%	$43.8922	$43.89	$43.90	$43.90
Purchase #6	$95.81	7.737%	$103.2228	$103.22	$103.20	$103.20
Purchase #7	$48.41	4.216%	$50.451	$50.45	$50.45	$50.50
7 purchase totals =	$643.37		$705.5679	$705.56	$705.60	$705.60