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	$59.39	8.817%	$64.6264	$64.63	$64.65	$64.60
Purchase #2	$167.44	10.800%	$185.5235	$185.52	$185.50	$185.50
Purchase #3	$19.90	7.796%	$21.4514	$21.45	$21.45	$21.50
Purchase #4	$21.55	6.605%	$22.9734	$22.97	$22.95	$23.00
Purchase #5	$20.55	3.421%	$21.253	$21.25	$21.25	$21.30
Purchase #6	$47.47	10.244%	$52.3328	$52.33	$52.35	$52.30
Purchase #7	$149.80	9.735%	$164.383	$164.38	$164.40	$164.40
7 purchase totals =	$486.10		$532.5435	$532.53	$532.55	$532.60