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	$174.39	12.688%	$196.5166	$196.52	$196.50	$196.50
Purchase #2	$38.46	7.353%	$41.288	$41.29	$41.30	$41.30
Purchase #3	$83.57	6.477%	$88.9828	$88.98	$89.00	$89.00
Purchase #4	$43.81	11.768%	$48.9656	$48.97	$48.95	$49.00
Purchase #5	$75.37	3.260%	$77.8271	$77.83	$77.85	$77.80
Purchase #6	$119.25	7.673%	$128.4001	$128.40	$128.40	$128.40
Purchase #7	$56.61	5.862%	$59.9285	$59.93	$59.95	$59.90
7 purchase totals =	$591.46		$641.9087	$641.92	$641.95	$641.90