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	$139.70	3.696%	$144.8633	$144.86	$144.85	$144.90
Purchase #2	$194.79	4.232%	$203.0335	$203.03	$203.05	$203.00
Purchase #3	$79.72	7.202%	$85.4614	$85.46	$85.45	$85.50
Purchase #4	$57.81	13.263%	$65.4773	$65.48	$65.50	$65.50
Purchase #5	$198.54	9.333%	$217.0697	$217.07	$217.05	$217.10
Purchase #6	$188.28	13.379%	$213.47	$213.47	$213.45	$213.50
Purchase #7	$193.48	11.500%	$215.7302	$215.73	$215.75	$215.70
7 purchase totals =	$1,052.32		$1,145.1054	$1,145.10	$1,145.10	$1,145.20