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	$192.66	12.433%	$216.6134	$216.61	$216.60	$216.60
Purchase #2	$196.91	10.436%	$217.4595	$217.46	$217.45	$217.50
Purchase #3	$131.32	11.534%	$146.4664	$146.47	$146.45	$146.50
Purchase #4	$117.67	11.223%	$130.8761	$130.88	$130.90	$130.90
Purchase #5	$248.65	11.133%	$276.3322	$276.33	$276.35	$276.30
Purchase #6	$104.80	3.282%	$108.2395	$108.24	$108.25	$108.20
Purchase #7	$209.46	8.596%	$227.4652	$227.47	$227.45	$227.50
7 purchase totals =	$1,201.47		$1,323.4523	$1,323.46	$1,323.45	$1,323.50