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	$43.72	11.325%	$48.6713	$48.67	$48.65	$48.70
Purchase #2	$123.81	3.206%	$127.7793	$127.78	$127.80	$127.80
Purchase #3	$217.25	4.455%	$226.9285	$226.93	$226.95	$226.90
Purchase #4	$99.81	3.124%	$102.9281	$102.93	$102.95	$102.90
Purchase #5	$130.46	13.542%	$148.1269	$148.13	$148.15	$148.10
Purchase #6	$238.25	6.539%	$253.8292	$253.83	$253.85	$253.80
Purchase #7	$169.64	7.723%	$182.7413	$182.74	$182.75	$182.70
7 purchase totals =	$1,022.94		$1,091.0046	$1,091.01	$1,091.10	$1,090.90