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	$71.40	3.409%	$73.834	$73.83	$73.85	$73.80
Purchase #2	$46.63	10.271%	$51.4194	$51.42	$51.40	$51.40
Purchase #3	$75.61	12.381%	$84.9713	$84.97	$84.95	$85.00
Purchase #4	$69.69	4.138%	$72.5738	$72.57	$72.55	$72.60
Purchase #5	$147.82	5.440%	$155.8614	$155.86	$155.85	$155.90
Purchase #6	$35.76	13.596%	$40.6219	$40.62	$40.60	$40.60
Purchase #7	$201.95	8.559%	$219.2349	$219.23	$219.25	$219.20
7 purchase totals =	$648.86		$698.5167	$698.50	$698.45	$698.50