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	$113.93	8.738%	$123.8852	$123.89	$123.90	$123.90
Purchase #2	$95.31	7.627%	$102.5793	$102.58	$102.60	$102.60
Purchase #3	$48.83	10.833%	$54.1198	$54.12	$54.10	$54.10
Purchase #4	$72.75	6.211%	$77.2685	$77.27	$77.25	$77.30
Purchase #5	$151.54	7.327%	$162.6433	$162.64	$162.65	$162.60
Purchase #6	$250.55	9.516%	$274.3923	$274.39	$274.40	$274.40
Purchase #7	$98.95	6.594%	$105.4748	$105.47	$105.45	$105.50
7 purchase totals =	$831.86		$900.3632	$900.36	$900.35	$900.40