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	$35.42	4.780%	$37.1131	$37.11	$37.10	$37.10
Purchase #2	$151.70	10.371%	$167.4328	$167.43	$167.45	$167.40
Purchase #3	$104.72	3.258%	$108.1318	$108.13	$108.15	$108.10
Purchase #4	$24.71	3.745%	$25.6354	$25.64	$25.65	$25.60
Purchase #5	$79.27	8.467%	$85.9818	$85.98	$86.00	$86.00
Purchase #6	$145.77	10.158%	$160.5773	$160.58	$160.60	$160.60
Purchase #7	$67.82	5.517%	$71.5616	$71.56	$71.55	$71.60
7 purchase totals =	$609.41		$656.4338	$656.43	$656.50	$656.40