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	$212.38	8.481%	$230.3919	$230.39	$230.40	$230.40
Purchase #2	$17.37	6.747%	$18.542	$18.54	$18.55	$18.50
Purchase #3	$19.33	9.504%	$21.1671	$21.17	$21.15	$21.20
Purchase #4	$37.95	12.801%	$42.808	$42.81	$42.80	$42.80
Purchase #5	$118.94	12.785%	$134.1465	$134.15	$134.15	$134.10
Purchase #6	$159.93	5.632%	$168.9373	$168.94	$168.95	$168.90
Purchase #7	$184.98	3.543%	$191.5338	$191.53	$191.55	$191.50
7 purchase totals =	$750.88		$807.5266	$807.53	$807.55	$807.40