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	$11.29	9.660%	$12.3806	$12.38	$12.40	$12.40
Purchase #2	$97.58	3.192%	$100.6948	$100.69	$100.70	$100.70
Purchase #3	$54.97	4.758%	$57.5855	$57.59	$57.60	$57.60
Purchase #4	$94.98	6.179%	$100.8488	$100.85	$100.85	$100.80
Purchase #5	$16.49	6.231%	$17.5175	$17.52	$17.50	$17.50
Purchase #6	$240.68	13.793%	$273.877	$273.88	$273.90	$273.90
Purchase #7	$117.80	6.644%	$125.6266	$125.63	$125.65	$125.60
7 purchase totals =	$633.79		$688.5308	$688.54	$688.60	$688.50