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	$140.73	10.653%	$155.722	$155.72	$155.70	$155.70
Purchase #2	$49.63	8.563%	$53.8798	$53.88	$53.90	$53.90
Purchase #3	$164.30	3.399%	$169.8846	$169.88	$169.90	$169.90
Purchase #4	$50.43	9.526%	$55.234	$55.23	$55.25	$55.20
Purchase #5	$140.52	7.797%	$151.4763	$151.48	$151.50	$151.50
Purchase #6	$124.48	5.576%	$131.421	$131.42	$131.40	$131.40
Purchase #7	$151.92	10.446%	$167.7896	$167.79	$167.80	$167.80
7 purchase totals =	$822.01		$885.4073	$885.40	$885.45	$885.40