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	$65.30	6.150%	$69.316	$69.32	$69.30	$69.30
Purchase #2	$35.46	8.837%	$38.5936	$38.59	$38.60	$38.60
Purchase #3	$165.45	3.788%	$171.7172	$171.72	$171.70	$171.70
Purchase #4	$100.86	4.131%	$105.0265	$105.03	$105.05	$105.00
Purchase #5	$155.50	4.625%	$162.6919	$162.69	$162.70	$162.70
Purchase #6	$24.32	13.353%	$27.5674	$27.57	$27.55	$27.60
Purchase #7	$124.83	7.614%	$134.3346	$134.33	$134.35	$134.30
7 purchase totals =	$671.72		$709.2472	$709.25	$709.25	$709.20