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	$62.95	12.210%	$70.6362	$70.64	$70.65	$70.60
Purchase #2	$241.80	7.244%	$259.316	$259.32	$259.30	$259.30
Purchase #3	$46.44	13.493%	$52.7061	$52.71	$52.70	$52.70
Purchase #4	$217.69	11.772%	$243.3165	$243.32	$243.30	$243.30
Purchase #5	$49.72	3.614%	$51.5169	$51.52	$51.50	$51.50
Purchase #6	$202.90	8.710%	$220.5726	$220.57	$220.55	$220.60
Purchase #7	$209.90	11.408%	$233.8454	$233.85	$233.85	$233.80
7 purchase totals =	$1,031.40		$1,131.9097	$1,131.93	$1,131.85	$1,131.80