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	$49.43	11.776%	$55.2509	$55.25	$55.25	$55.30
Purchase #2	$190.86	11.848%	$213.4731	$213.47	$213.45	$213.50
Purchase #3	$69.79	3.197%	$72.0212	$72.02	$72.00	$72.00
Purchase #4	$200.80	7.873%	$216.609	$216.61	$216.60	$216.60
Purchase #5	$147.42	6.144%	$156.4775	$156.48	$156.50	$156.50
Purchase #6	$88.34	3.640%	$91.5556	$91.56	$91.55	$91.60
Purchase #7	$233.27	12.323%	$262.0159	$262.02	$262.00	$262.00
7 purchase totals =	$979.91		$1,067.4032	$1,067.41	$1,067.35	$1,067.50