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	$127.95	10.850%	$141.8326	$141.83	$141.85	$141.80
Purchase #2	$142.63	4.702%	$149.3365	$149.34	$149.35	$149.30
Purchase #3	$109.83	13.724%	$124.9031	$124.90	$124.90	$124.90
Purchase #4	$36.58	10.657%	$40.4783	$40.48	$40.50	$40.50
Purchase #5	$59.99	5.432%	$63.2487	$63.25	$63.25	$63.20
Purchase #6	$85.58	4.768%	$89.6605	$89.66	$89.65	$89.70
Purchase #7	$77.38	5.107%	$81.3318	$81.33	$81.35	$81.30
7 purchase totals =	$639.94		$690.7915	$690.79	$690.85	$690.70