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	$191.45	4.419%	$199.9102	$199.91	$199.90	$199.90
Purchase #2	$227.76	11.719%	$254.4512	$254.45	$254.45	$254.50
Purchase #3	$8.83	4.776%	$9.2517	$9.25	$9.25	$9.30
Purchase #4	$237.87	7.377%	$255.4177	$255.42	$255.40	$255.40
Purchase #5	$59.62	10.210%	$65.7072	$65.71	$65.70	$65.70
Purchase #6	$41.26	10.446%	$45.57	$45.57	$45.55	$45.60
Purchase #7	$213.79	13.625%	$242.9189	$242.92	$242.90	$242.90
7 purchase totals =	$980.58		$1,073.2269	$1,073.23	$1,073.15	$1,073.30