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	$106.84	4.393%	$111.5335	$111.53	$111.55	$111.50
Purchase #2	$179.83	11.508%	$200.5248	$200.52	$200.50	$200.50
Purchase #3	$37.85	4.669%	$39.6172	$39.62	$39.60	$39.60
Purchase #4	$129.54	8.533%	$140.5936	$140.59	$140.60	$140.60
Purchase #5	$206.87	8.387%	$224.2202	$224.22	$224.20	$224.20
Purchase #6	$33.97	5.153%	$35.7205	$35.72	$35.70	$35.70
Purchase #7	$228.82	13.198%	$259.0197	$259.02	$259.00	$259.00
7 purchase totals =	$923.72		$1,011.2295	$1,011.22	$1,011.15	$1,011.10