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	$247.46	10.416%	$273.2354	$273.24	$273.25	$273.20
Purchase #2	$119.63	10.391%	$132.0608	$132.06	$132.05	$132.10
Purchase #3	$68.57	3.678%	$71.092	$71.09	$71.10	$71.10
Purchase #4	$118.31	8.390%	$128.2362	$128.24	$128.25	$128.20
Purchase #5	$244.77	12.130%	$274.4606	$274.46	$274.45	$274.50
Purchase #6	$166.46	8.268%	$180.2229	$180.22	$180.20	$180.20
Purchase #7	$131.73	7.229%	$141.2528	$141.25	$141.25	$141.30
7 purchase totals =	$1,096.93		$1,200.5607	$1,200.56	$1,200.55	$1,200.60