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	$93.59	6.790%	$99.9448	$99.94	$99.95	$99.90
Purchase #2	$27.56	12.736%	$31.07	$31.07	$31.05	$31.10
Purchase #3	$65.69	8.466%	$71.2513	$71.25	$71.25	$71.30
Purchase #4	$36.75	5.273%	$38.6878	$38.69	$38.70	$38.70
Purchase #5	$77.27	13.371%	$87.6018	$87.60	$87.60	$87.60
Purchase #6	$31.82	5.292%	$33.5039	$33.50	$33.50	$33.50
Purchase #7	$63.69	6.395%	$67.763	$67.76	$67.75	$67.80
7 purchase totals =	$396.37		$429.8226	$429.81	$429.80	$429.90