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	$102.81	11.727%	$114.8665	$114.87	$114.85	$114.90
Purchase #2	$172.59	11.440%	$192.3343	$192.33	$192.35	$192.30
Purchase #3	$138.46	7.260%	$148.5122	$148.51	$148.50	$148.50
Purchase #4	$90.84	4.366%	$94.8061	$94.81	$94.80	$94.80
Purchase #5	$174.89	11.586%	$195.1528	$195.15	$195.15	$195.20
Purchase #6	$68.63	4.813%	$71.9332	$71.93	$71.95	$71.90
Purchase #7	$93.41	3.697%	$96.8634	$96.86	$96.85	$96.90
7 purchase totals =	$841.63		$914.4685	$914.46	$914.45	$914.50