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	$246.59	8.341%	$267.1581	$267.16	$267.15	$267.20
Purchase #2	$129.46	13.489%	$146.9229	$146.92	$146.90	$146.90
Purchase #3	$99.57	4.458%	$104.0088	$104.01	$104.00	$104.00
Purchase #4	$19.80	3.529%	$20.4987	$20.50	$20.50	$20.50
Purchase #5	$197.78	12.715%	$222.9277	$222.93	$222.95	$222.90
Purchase #6	$42.25	7.404%	$45.3782	$45.38	$45.40	$45.40
Purchase #7	$164.27	6.700%	$175.2761	$175.28	$175.30	$175.30
7 purchase totals =	$899.72		$982.1705	$982.18	$982.20	$982.20