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	$56.83	4.402%	$59.3317	$59.33	$59.35	$59.30
Purchase #2	$125.30	8.704%	$136.2061	$136.21	$136.20	$136.20
Purchase #3	$11.36	10.273%	$12.527	$12.53	$12.55	$12.50
Purchase #4	$246.59	5.159%	$259.3116	$259.31	$259.30	$259.30
Purchase #5	$138.59	3.420%	$143.3298	$143.33	$143.35	$143.30
Purchase #6	$36.79	9.787%	$40.3906	$40.39	$40.40	$40.40
Purchase #7	$139.79	11.253%	$155.5206	$155.52	$155.50	$155.50
7 purchase totals =	$755.25		$806.6174	$806.62	$806.65	$806.50