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	$170.93	12.259%	$191.8843	$191.88	$191.90	$191.90
Purchase #2	$215.72	8.249%	$233.5147	$233.51	$233.50	$233.50
Purchase #3	$11.26	12.229%	$12.637	$12.64	$12.65	$12.60
Purchase #4	$16.75	13.308%	$18.9791	$18.98	$19.00	$19.00
Purchase #5	$197.36	11.620%	$220.2932	$220.29	$220.30	$220.30
Purchase #6	$39.86	13.843%	$45.3778	$45.38	$45.40	$45.40
Purchase #7	$131.45	10.558%	$145.3285	$145.33	$145.35	$145.30
7 purchase totals =	$783.33		$868.0146	$868.01	$868.10	$868.00