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	$91.30	13.869%	$103.9624	$103.96	$103.95	$104.00
Purchase #2	$79.38	12.743%	$89.4954	$89.50	$89.50	$89.50
Purchase #3	$65.78	8.729%	$71.5219	$71.52	$71.50	$71.50
Purchase #4	$43.98	12.553%	$49.5008	$49.50	$49.50	$49.50
Purchase #5	$219.60	10.115%	$241.8125	$241.81	$241.80	$241.80
Purchase #6	$225.47	4.799%	$236.2903	$236.29	$236.30	$236.30
Purchase #7	$125.99	6.776%	$134.5271	$134.53	$134.55	$134.50
7 purchase totals =	$851.50		$927.1104	$927.11	$927.10	$927.10