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	$29.43	11.556%	$32.8309	$32.83	$32.85	$32.80
Purchase #2	$117.25	6.863%	$125.2969	$125.30	$125.30	$125.30
Purchase #3	$31.47	5.191%	$33.1036	$33.10	$33.10	$33.10
Purchase #4	$222.89	6.744%	$237.9217	$237.92	$237.90	$237.90
Purchase #5	$189.72	4.662%	$198.5647	$198.56	$198.55	$198.60
Purchase #6	$177.36	12.645%	$199.7872	$199.79	$199.80	$199.80
Purchase #7	$215.48	8.501%	$233.798	$233.80	$233.80	$233.80
7 purchase totals =	$983.60		$1,061.3030	$1,061.30	$1,061.30	$1,061.30