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	$38.67	13.612%	$43.9338	$43.93	$43.95	$43.90
Purchase #2	$18.50	4.817%	$19.3911	$19.39	$19.40	$19.40
Purchase #3	$74.65	10.456%	$82.4554	$82.46	$82.45	$82.50
Purchase #4	$174.31	12.547%	$196.1807	$196.18	$196.20	$196.20
Purchase #5	$164.96	6.702%	$176.0156	$176.02	$176.00	$176.00
Purchase #6	$17.83	5.155%	$18.7491	$18.75	$18.75	$18.70
Purchase #7	$125.45	7.214%	$134.5	$134.50	$134.50	$134.50
7 purchase totals =	$614.37		$671.2257	$671.23	$671.25	$671.20