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	$238.37	11.629%	$266.09	$266.09	$266.10	$266.10
Purchase #2	$190.43	4.570%	$199.1327	$199.13	$199.15	$199.10
Purchase #3	$80.29	7.861%	$86.6016	$86.60	$86.60	$86.60
Purchase #4	$58.32	5.346%	$61.4378	$61.44	$61.45	$61.40
Purchase #5	$135.49	6.475%	$144.263	$144.26	$144.25	$144.30
Purchase #6	$159.76	5.516%	$168.5724	$168.57	$168.55	$168.60
Purchase #7	$140.35	6.124%	$148.945	$148.95	$148.95	$148.90
7 purchase totals =	$1,003.01		$1,075.0425	$1,075.04	$1,075.05	$1,075.00