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	$43.50	4.851%	$45.6102	$45.61	$45.60	$45.60
Purchase #2	$28.54	13.742%	$32.462	$32.46	$32.45	$32.50
Purchase #3	$114.61	9.513%	$125.5128	$125.51	$125.50	$125.50
Purchase #4	$223.80	6.583%	$238.5328	$238.53	$238.55	$238.50
Purchase #5	$219.93	6.615%	$234.4784	$234.48	$234.50	$234.50
Purchase #6	$156.63	13.864%	$178.3452	$178.35	$178.35	$178.30
Purchase #7	$14.60	13.366%	$16.5514	$16.55	$16.55	$16.60
7 purchase totals =	$801.61		$871.4928	$871.49	$871.50	$871.50