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	$124.92	7.190%	$133.9017	$133.90	$133.90	$133.90
Purchase #2	$93.67	12.292%	$105.1839	$105.18	$105.20	$105.20
Purchase #3	$144.76	4.389%	$151.1135	$151.11	$151.10	$151.10
Purchase #4	$108.47	6.691%	$115.7277	$115.73	$115.75	$115.70
Purchase #5	$155.65	11.445%	$173.4641	$173.46	$173.45	$173.50
Purchase #6	$117.79	11.772%	$131.6562	$131.66	$131.65	$131.70
Purchase #7	$198.27	5.317%	$208.812	$208.81	$208.80	$208.80
7 purchase totals =	$943.53		$1,019.8591	$1,019.85	$1,019.85	$1,019.90