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	$147.68	3.456%	$152.7838	$152.78	$152.80	$152.80
Purchase #2	$70.94	5.744%	$75.0148	$75.01	$75.00	$75.00
Purchase #3	$98.58	3.804%	$102.33	$102.33	$102.35	$102.30
Purchase #4	$95.78	7.114%	$102.5938	$102.59	$102.60	$102.60
Purchase #5	$29.57	7.825%	$31.8839	$31.88	$31.90	$31.90
Purchase #6	$102.57	7.135%	$109.8884	$109.89	$109.90	$109.90
Purchase #7	$53.47	5.602%	$56.4654	$56.47	$56.45	$56.50
7 purchase totals =	$598.59		$630.9601	$630.95	$631.00	$631.00