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	$48.75	11.691%	$54.4494	$54.45	$54.45	$54.40
Purchase #2	$157.41	9.541%	$172.4285	$172.43	$172.45	$172.40
Purchase #3	$239.62	12.242%	$268.9543	$268.95	$268.95	$269.00
Purchase #4	$177.71	10.630%	$196.6006	$196.60	$196.60	$196.60
Purchase #5	$23.72	9.127%	$25.8849	$25.88	$25.90	$25.90
Purchase #6	$110.90	13.521%	$125.8948	$125.89	$125.90	$125.90
Purchase #7	$187.44	9.182%	$204.6507	$204.65	$204.65	$204.70
7 purchase totals =	$945.55		$1,048.8632	$1,048.85	$1,048.90	$1,048.90