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	$63.57	4.292%	$66.2984	$66.30	$66.30	$66.30
Purchase #2	$30.49	9.822%	$33.4847	$33.48	$33.50	$33.50
Purchase #3	$157.63	8.393%	$170.8599	$170.86	$170.85	$170.90
Purchase #4	$155.73	4.121%	$162.1476	$162.15	$162.15	$162.10
Purchase #5	$39.95	7.537%	$42.961	$42.96	$42.95	$43.00
Purchase #6	$56.47	5.861%	$59.7797	$59.78	$59.80	$59.80
Purchase #7	$171.74	6.158%	$182.3157	$182.32	$182.30	$182.30
7 purchase totals =	$675.58		$717.8470	$717.85	$717.85	$717.90