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	$174.58	13.421%	$198.0104	$198.01	$198.00	$198.00
Purchase #2	$77.89	9.748%	$85.4827	$85.48	$85.50	$85.50
Purchase #3	$241.96	7.387%	$259.8336	$259.83	$259.85	$259.80
Purchase #4	$120.80	4.765%	$126.5561	$126.56	$126.55	$126.60
Purchase #5	$230.61	8.224%	$249.5754	$249.58	$249.60	$249.60
Purchase #6	$142.50	6.235%	$151.3849	$151.38	$151.40	$151.40
Purchase #7	$84.68	5.474%	$89.3154	$89.32	$89.30	$89.30
7 purchase totals =	$1,073.02		$1,160.1585	$1,160.16	$1,160.20	$1,160.20