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	$31.40	9.873%	$34.5001	$34.50	$34.50	$34.50
Purchase #2	$193.52	9.498%	$211.9005	$211.90	$211.90	$211.90
Purchase #3	$35.70	10.202%	$39.3421	$39.34	$39.35	$39.30
Purchase #4	$180.29	8.287%	$195.2306	$195.23	$195.25	$195.20
Purchase #5	$228.51	13.562%	$259.5005	$259.50	$259.50	$259.50
Purchase #6	$52.84	12.597%	$59.4963	$59.50	$59.50	$59.50
Purchase #7	$241.83	6.846%	$258.3857	$258.39	$258.40	$258.40
7 purchase totals =	$964.09		$1,058.3558	$1,058.36	$1,058.40	$1,058.30