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	$142.50	13.773%	$162.1265	$162.13	$162.15	$162.10
Purchase #2	$192.48	13.257%	$217.9971	$218.00	$218.00	$218.00
Purchase #3	$29.56	13.710%	$33.6127	$33.61	$33.60	$33.60
Purchase #4	$80.37	12.676%	$90.5577	$90.56	$90.55	$90.60
Purchase #5	$147.52	5.488%	$155.6159	$155.62	$155.60	$155.60
Purchase #6	$205.62	11.690%	$229.657	$229.66	$229.65	$229.70
Purchase #7	$182.69	12.770%	$206.0195	$206.02	$206.00	$206.00
7 purchase totals =	$980.74		$1,095.5864	$1,095.60	$1,095.55	$1,095.60