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	$155.65	3.795%	$161.5569	$161.56	$161.55	$161.60
Purchase #2	$111.54	12.587%	$125.5795	$125.58	$125.60	$125.60
Purchase #3	$61.65	12.619%	$69.4296	$69.43	$69.45	$69.40
Purchase #4	$250.83	4.828%	$262.9401	$262.94	$262.95	$262.90
Purchase #5	$64.77	12.372%	$72.7833	$72.78	$72.80	$72.80
Purchase #6	$120.56	8.239%	$130.4929	$130.49	$130.50	$130.50
Purchase #7	$94.96	11.371%	$105.7579	$105.76	$105.75	$105.80
7 purchase totals =	$859.96		$928.5402	$928.54	$928.60	$928.60