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	$72.42	8.854%	$78.8321	$78.83	$78.85	$78.80
Purchase #2	$113.40	11.280%	$126.1915	$126.19	$126.20	$126.20
Purchase #3	$67.70	13.442%	$76.8002	$76.80	$76.80	$76.80
Purchase #4	$240.27	4.658%	$251.4618	$251.46	$251.45	$251.50
Purchase #5	$66.28	13.181%	$75.0164	$75.02	$75.00	$75.00
Purchase #6	$59.59	13.183%	$67.4457	$67.45	$67.45	$67.40
Purchase #7	$218.45	4.322%	$227.8914	$227.89	$227.90	$227.90
7 purchase totals =	$838.11		$903.6391	$903.64	$903.65	$903.60