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	$217.67	5.452%	$229.5374	$229.54	$229.55	$229.50
Purchase #2	$115.66	6.458%	$123.1293	$123.13	$123.15	$123.10
Purchase #3	$216.80	3.695%	$224.8108	$224.81	$224.80	$224.80
Purchase #4	$169.40	11.261%	$188.4761	$188.48	$188.50	$188.50
Purchase #5	$75.55	4.216%	$78.7352	$78.74	$78.75	$78.70
Purchase #6	$16.93	10.231%	$18.6621	$18.66	$18.65	$18.70
Purchase #7	$130.30	9.434%	$142.5925	$142.59	$142.60	$142.60
7 purchase totals =	$942.31		$1,005.9434	$1,005.95	$1,006.00	$1,005.90