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	$9.84	9.583%	$10.783	$10.78	$10.80	$10.80
Purchase #2	$18.77	13.554%	$21.3141	$21.31	$21.30	$21.30
Purchase #3	$12.48	3.822%	$12.957	$12.96	$12.95	$13.00
Purchase #4	$94.59	4.659%	$98.9969	$99.00	$99.00	$99.00
Purchase #5	$37.48	10.647%	$41.4705	$41.47	$41.45	$41.50
Purchase #6	$104.37	13.524%	$118.485	$118.49	$118.50	$118.50
Purchase #7	$131.77	3.614%	$136.5322	$136.53	$136.55	$136.50
7 purchase totals =	$409.30		$440.5387	$440.54	$440.55	$440.60