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	$160.31	5.125%	$168.5259	$168.53	$168.55	$168.50
Purchase #2	$159.31	5.395%	$167.9048	$167.90	$167.90	$167.90
Purchase #3	$59.94	3.219%	$61.8695	$61.87	$61.85	$61.90
Purchase #4	$107.80	5.516%	$113.7462	$113.75	$113.75	$113.70
Purchase #5	$196.29	9.591%	$215.1162	$215.12	$215.10	$215.10
Purchase #6	$102.76	9.591%	$112.6157	$112.62	$112.60	$112.60
Purchase #7	$31.83	4.587%	$33.29	$33.29	$33.30	$33.30
7 purchase totals =	$818.24		$873.0683	$873.08	$873.05	$873.00