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	$56.99	7.833%	$61.454	$61.45	$61.45	$61.50
Purchase #2	$101.77	4.228%	$106.0728	$106.07	$106.05	$106.10
Purchase #3	$33.25	11.162%	$36.9614	$36.96	$36.95	$37.00
Purchase #4	$116.32	6.427%	$123.7959	$123.80	$123.80	$123.80
Purchase #5	$41.79	12.502%	$47.0146	$47.01	$47.00	$47.00
Purchase #6	$56.92	3.665%	$59.0061	$59.01	$59.00	$59.00
Purchase #7	$193.83	11.627%	$216.3666	$216.37	$216.35	$216.40
7 purchase totals =	$600.87		$650.6714	$650.67	$650.60	$650.80