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	$206.66	10.314%	$227.9749	$227.97	$227.95	$228.00
Purchase #2	$177.41	4.624%	$185.6134	$185.61	$185.60	$185.60
Purchase #3	$29.72	10.179%	$32.7452	$32.75	$32.75	$32.70
Purchase #4	$181.96	8.238%	$196.9499	$196.95	$196.95	$196.90
Purchase #5	$126.95	13.594%	$144.2076	$144.21	$144.20	$144.20
Purchase #6	$31.36	12.618%	$35.317	$35.32	$35.30	$35.30
Purchase #7	$245.81	10.804%	$272.3673	$272.37	$272.35	$272.40
7 purchase totals =	$999.87		$1,095.1753	$1,095.18	$1,095.10	$1,095.10