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	$102.31	12.348%	$114.9432	$114.94	$114.95	$114.90
Purchase #2	$66.94	7.498%	$71.9592	$71.96	$71.95	$72.00
Purchase #3	$146.71	9.580%	$160.7648	$160.76	$160.75	$160.80
Purchase #4	$111.51	7.356%	$119.7127	$119.71	$119.70	$119.70
Purchase #5	$37.86	11.159%	$42.0848	$42.08	$42.10	$42.10
Purchase #6	$233.51	11.277%	$259.8429	$259.84	$259.85	$259.80
Purchase #7	$233.75	3.527%	$241.9944	$241.99	$242.00	$242.00
7 purchase totals =	$932.59		$1,011.3020	$1,011.28	$1,011.30	$1,011.30