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	$165.70	3.469%	$171.4481	$171.45	$171.45	$171.40
Purchase #2	$199.87	11.846%	$223.5466	$223.55	$223.55	$223.50
Purchase #3	$119.29	9.465%	$130.5808	$130.58	$130.60	$130.60
Purchase #4	$130.69	9.480%	$143.0794	$143.08	$143.10	$143.10
Purchase #5	$49.50	4.244%	$51.6008	$51.60	$51.60	$51.60
Purchase #6	$176.90	5.676%	$186.9408	$186.94	$186.95	$186.90
Purchase #7	$227.87	11.526%	$254.1343	$254.13	$254.15	$254.10
7 purchase totals =	$1,069.82		$1,161.3308	$1,161.33	$1,161.40	$1,161.20