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	$154.88	11.628%	$172.8894	$172.89	$172.90	$172.90
Purchase #2	$192.96	6.520%	$205.541	$205.54	$205.55	$205.50
Purchase #3	$215.91	8.297%	$233.8241	$233.82	$233.80	$233.80
Purchase #4	$123.72	4.256%	$128.9855	$128.99	$129.00	$129.00
Purchase #5	$14.80	8.227%	$16.0176	$16.02	$16.00	$16.00
Purchase #6	$41.92	8.141%	$45.3327	$45.33	$45.35	$45.30
Purchase #7	$169.27	5.717%	$178.9472	$178.95	$178.95	$178.90
7 purchase totals =	$913.46		$981.5375	$981.54	$981.55	$981.40