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	$71.47	7.119%	$76.5579	$76.56	$76.55	$76.60
Purchase #2	$34.56	3.708%	$35.8415	$35.84	$35.85	$35.80
Purchase #3	$70.42	11.595%	$78.5852	$78.59	$78.60	$78.60
Purchase #4	$180.35	4.148%	$187.8309	$187.83	$187.85	$187.80
Purchase #5	$177.79	5.419%	$187.4244	$187.42	$187.40	$187.40
Purchase #6	$86.59	6.641%	$92.3404	$92.34	$92.35	$92.30
Purchase #7	$179.45	5.240%	$188.8532	$188.85	$188.85	$188.90
7 purchase totals =	$800.63		$847.4335	$847.43	$847.45	$847.40