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	$49.59	10.120%	$54.6085	$54.61	$54.60	$54.60
Purchase #2	$165.25	9.203%	$180.458	$180.46	$180.45	$180.50
Purchase #3	$49.45	11.424%	$55.0992	$55.10	$55.10	$55.10
Purchase #4	$208.47	11.660%	$232.7776	$232.78	$232.80	$232.80
Purchase #5	$229.86	3.326%	$237.5051	$237.51	$237.50	$237.50
Purchase #6	$237.46	7.171%	$254.4883	$254.49	$254.50	$254.50
Purchase #7	$167.60	10.655%	$185.4578	$185.46	$185.45	$185.50
7 purchase totals =	$1,107.68		$1,200.3945	$1,200.41	$1,200.40	$1,200.50