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	$202.88	7.410%	$217.9134	$217.91	$217.90	$217.90
Purchase #2	$142.71	6.447%	$151.9105	$151.91	$151.90	$151.90
Purchase #3	$191.47	13.773%	$217.8412	$217.84	$217.85	$217.80
Purchase #4	$225.54	11.452%	$251.3688	$251.37	$251.35	$251.40
Purchase #5	$26.33	5.768%	$27.8487	$27.85	$27.85	$27.80
Purchase #6	$179.89	5.690%	$190.1257	$190.13	$190.15	$190.10
Purchase #7	$49.26	6.798%	$52.6087	$52.61	$52.60	$52.60
7 purchase totals =	$1,018.08		$1,109.6170	$1,109.62	$1,109.60	$1,109.50