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	$54.43	9.344%	$59.5159	$59.52	$59.50	$59.50
Purchase #2	$164.66	12.287%	$184.8918	$184.89	$184.90	$184.90
Purchase #3	$179.41	10.777%	$198.745	$198.75	$198.75	$198.70
Purchase #4	$11.53	7.518%	$12.3968	$12.40	$12.40	$12.40
Purchase #5	$71.44	13.531%	$81.1065	$81.11	$81.10	$81.10
Purchase #6	$115.36	7.463%	$123.9693	$123.97	$123.95	$124.00
Purchase #7	$92.85	7.604%	$99.9103	$99.91	$99.90	$99.90
7 purchase totals =	$689.68		$760.5356	$760.55	$760.50	$760.50