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	$80.60	11.107%	$89.5522	$89.55	$89.55	$89.60
Purchase #2	$67.95	5.170%	$71.463	$71.46	$71.45	$71.50
Purchase #3	$33.93	6.316%	$36.073	$36.07	$36.05	$36.10
Purchase #4	$225.81	5.457%	$238.1325	$238.13	$238.15	$238.10
Purchase #5	$24.32	6.728%	$25.9562	$25.96	$25.95	$26.00
Purchase #6	$198.65	3.663%	$205.9265	$205.93	$205.95	$205.90
Purchase #7	$146.85	9.448%	$160.7244	$160.72	$160.70	$160.70
7 purchase totals =	$778.11		$827.8278	$827.82	$827.80	$827.90