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	$61.34	4.147%	$63.8838	$63.88	$63.90	$63.90
Purchase #2	$31.89	9.779%	$35.0085	$35.01	$35.00	$35.00
Purchase #3	$151.76	8.729%	$165.0071	$165.01	$165.00	$165.00
Purchase #4	$246.72	5.187%	$259.5174	$259.52	$259.50	$259.50
Purchase #5	$98.54	5.651%	$104.1085	$104.11	$104.10	$104.10
Purchase #6	$19.63	9.458%	$21.4866	$21.49	$21.50	$21.50
Purchase #7	$40.51	7.402%	$43.5086	$43.51	$43.50	$43.50
7 purchase totals =	$650.39		$692.5205	$692.53	$692.50	$692.50