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	$124.55	13.134%	$140.9084	$140.91	$140.90	$140.90
Purchase #2	$82.33	12.177%	$92.3553	$92.36	$92.35	$92.40
Purchase #3	$69.36	13.275%	$78.5675	$78.57	$78.55	$78.60
Purchase #4	$100.83	3.716%	$104.5768	$104.58	$104.60	$104.60
Purchase #5	$48.71	6.440%	$51.8469	$51.85	$51.85	$51.80
Purchase #6	$21.67	4.724%	$22.6937	$22.69	$22.70	$22.70
Purchase #7	$182.61	12.789%	$205.964	$205.96	$205.95	$206.00
7 purchase totals =	$630.06		$696.9126	$696.92	$696.90	$697.00