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	$210.29	8.473%	$228.1079	$228.11	$228.10	$228.10
Purchase #2	$24.75	11.489%	$27.5935	$27.59	$27.60	$27.60
Purchase #3	$30.54	3.444%	$31.5918	$31.59	$31.60	$31.60
Purchase #4	$105.62	12.631%	$118.9609	$118.96	$118.95	$119.00
Purchase #5	$172.35	7.674%	$185.5761	$185.58	$185.60	$185.60
Purchase #6	$154.37	4.831%	$161.8276	$161.83	$161.85	$161.80
Purchase #7	$91.52	3.697%	$94.9035	$94.90	$94.90	$94.90
7 purchase totals =	$789.44		$848.5613	$848.56	$848.60	$848.60