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	$44.36	13.440%	$50.322	$50.32	$50.30	$50.30
Purchase #2	$64.97	13.507%	$73.7455	$73.75	$73.75	$73.70
Purchase #3	$59.36	9.467%	$64.9796	$64.98	$65.00	$65.00
Purchase #4	$54.33	9.453%	$59.4658	$59.47	$59.45	$59.50
Purchase #5	$32.54	9.708%	$35.699	$35.70	$35.70	$35.70
Purchase #6	$158.51	3.791%	$164.5191	$164.52	$164.50	$164.50
Purchase #7	$40.48	12.783%	$45.6546	$45.65	$45.65	$45.70
7 purchase totals =	$454.55		$494.3856	$494.39	$494.35	$494.40