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	$109.25	8.518%	$118.5559	$118.56	$118.55	$118.60
Purchase #2	$84.35	5.572%	$89.05	$89.05	$89.05	$89.10
Purchase #3	$196.83	10.769%	$218.0266	$218.03	$218.05	$218.00
Purchase #4	$82.32	8.335%	$89.1814	$89.18	$89.20	$89.20
Purchase #5	$201.57	11.363%	$224.4744	$224.47	$224.45	$224.50
Purchase #6	$33.85	8.569%	$36.7506	$36.75	$36.75	$36.80
Purchase #7	$73.47	7.382%	$78.8936	$78.89	$78.90	$78.90
7 purchase totals =	$781.64		$854.9325	$854.93	$854.95	$855.10