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	$248.92	13.538%	$282.6188	$282.62	$282.60	$282.60
Purchase #2	$41.67	5.583%	$43.9964	$44.00	$44.00	$44.00
Purchase #3	$110.96	6.332%	$117.986	$117.99	$118.00	$118.00
Purchase #4	$79.87	7.554%	$85.9034	$85.90	$85.90	$85.90
Purchase #5	$157.60	13.316%	$178.586	$178.59	$178.60	$178.60
Purchase #6	$69.83	11.732%	$78.0225	$78.02	$78.00	$78.00
Purchase #7	$206.72	10.711%	$228.8618	$228.86	$228.85	$228.90
7 purchase totals =	$915.57		$1,015.9749	$1,015.98	$1,015.95	$1,016.00