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	$76.99	10.274%	$84.9	$84.90	$84.90	$84.90
Purchase #2	$121.57	12.436%	$136.6884	$136.69	$136.70	$136.70
Purchase #3	$104.29	11.229%	$116.0007	$116.00	$116.00	$116.00
Purchase #4	$173.64	3.578%	$179.8528	$179.85	$179.85	$179.90
Purchase #5	$35.90	4.769%	$37.6121	$37.61	$37.60	$37.60
Purchase #6	$114.42	12.652%	$128.8964	$128.90	$128.90	$128.90
Purchase #7	$125.76	4.401%	$131.2947	$131.29	$131.30	$131.30
7 purchase totals =	$752.57		$815.2451	$815.24	$815.25	$815.30