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	$92.88	6.430%	$98.8522	$98.85	$98.85	$98.90
Purchase #2	$190.69	13.811%	$217.0262	$217.03	$217.05	$217.00
Purchase #3	$131.50	6.110%	$139.5347	$139.53	$139.55	$139.50
Purchase #4	$167.42	7.259%	$179.573	$179.57	$179.55	$179.60
Purchase #5	$111.29	7.781%	$119.9495	$119.95	$119.95	$119.90
Purchase #6	$149.53	10.509%	$165.2441	$165.24	$165.25	$165.20
Purchase #7	$204.47	12.571%	$230.1739	$230.17	$230.15	$230.20
7 purchase totals =	$1,047.78		$1,150.3536	$1,150.34	$1,150.35	$1,150.30