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	$116.40	6.354%	$123.7961	$123.80	$123.80	$123.80
Purchase #2	$164.41	6.768%	$175.5373	$175.54	$175.55	$175.50
Purchase #3	$74.57	10.275%	$82.2321	$82.23	$82.25	$82.20
Purchase #4	$105.76	3.822%	$109.8021	$109.80	$109.80	$109.80
Purchase #5	$92.48	8.562%	$100.3981	$100.40	$100.40	$100.40
Purchase #6	$125.69	6.119%	$133.381	$133.38	$133.40	$133.40
Purchase #7	$34.58	3.526%	$35.7993	$35.80	$35.80	$35.80
7 purchase totals =	$713.89		$760.9460	$760.95	$761.00	$760.90