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	$81.43	8.553%	$88.3947	$88.39	$88.40	$88.40
Purchase #2	$128.45	13.665%	$146.0027	$146.00	$146.00	$146.00
Purchase #3	$39.89	6.485%	$42.4769	$42.48	$42.50	$42.50
Purchase #4	$38.66	13.448%	$43.859	$43.86	$43.85	$43.90
Purchase #5	$130.89	8.539%	$142.0667	$142.07	$142.05	$142.10
Purchase #6	$11.41	3.277%	$11.7839	$11.78	$11.80	$11.80
Purchase #7	$223.47	7.818%	$240.9409	$240.94	$240.95	$240.90
7 purchase totals =	$654.20		$715.5248	$715.52	$715.55	$715.60