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	$207.84	13.353%	$235.5929	$235.59	$235.60	$235.60
Purchase #2	$60.39	7.626%	$64.9953	$65.00	$65.00	$65.00
Purchase #3	$44.72	9.535%	$48.9841	$48.98	$49.00	$49.00
Purchase #4	$137.30	10.566%	$151.8071	$151.81	$151.80	$151.80
Purchase #5	$233.47	8.619%	$253.5928	$253.59	$253.60	$253.60
Purchase #6	$71.48	9.834%	$78.5093	$78.51	$78.50	$78.50
Purchase #7	$153.90	11.292%	$171.2784	$171.28	$171.30	$171.30
7 purchase totals =	$909.10		$1,004.7599	$1,004.76	$1,004.80	$1,004.80