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	$135.47	8.159%	$146.523	$146.52	$146.50	$146.50
Purchase #2	$29.64	9.121%	$32.3435	$32.34	$32.35	$32.30
Purchase #3	$216.41	9.263%	$236.4561	$236.46	$236.45	$236.50
Purchase #4	$21.42	11.445%	$23.8715	$23.87	$23.85	$23.90
Purchase #5	$249.73	12.446%	$280.8114	$280.81	$280.80	$280.80
Purchase #6	$102.71	8.819%	$111.768	$111.77	$111.75	$111.80
Purchase #7	$70.41	11.827%	$78.7374	$78.74	$78.75	$78.70
7 purchase totals =	$825.79		$910.5109	$910.51	$910.45	$910.50