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	$65.85	9.834%	$72.3257	$72.33	$72.35	$72.30
Purchase #2	$125.69	12.482%	$141.3786	$141.38	$141.40	$141.40
Purchase #3	$90.92	3.782%	$94.3586	$94.36	$94.35	$94.40
Purchase #4	$82.43	4.359%	$86.0231	$86.02	$86.00	$86.00
Purchase #5	$234.48	7.677%	$252.481	$252.48	$252.50	$252.50
Purchase #6	$62.73	5.424%	$66.1325	$66.13	$66.15	$66.10
Purchase #7	$248.84	8.139%	$269.0931	$269.09	$269.10	$269.10
7 purchase totals =	$910.94		$981.7926	$981.79	$981.85	$981.80