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	$103.72	8.474%	$112.5092	$112.51	$112.50	$112.50
Purchase #2	$117.98	4.679%	$123.5003	$123.50	$123.50	$123.50
Purchase #3	$168.76	12.825%	$190.4035	$190.40	$190.40	$190.40
Purchase #4	$41.28	10.458%	$45.5971	$45.60	$45.60	$45.60
Purchase #5	$169.33	13.324%	$191.8915	$191.89	$191.90	$191.90
Purchase #6	$5.61	13.804%	$6.3844	$6.38	$6.40	$6.40
Purchase #7	$54.27	3.123%	$55.9649	$55.96	$55.95	$56.00
7 purchase totals =	$660.95		$726.2509	$726.24	$726.25	$726.30